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71bfa161 JA |
1 | Table of contents |
2 | ----------------- | |
3 | ||
4 | 1. Overview | |
5 | 2. How fio works | |
6 | 3. Running fio | |
7 | 4. Job file format | |
8 | 5. Detailed list of parameters | |
9 | 6. Normal output | |
10 | 7. Terse output | |
25c8b9d7 | 11 | 8. Trace file format |
43f09da1 | 12 | 9. CPU idleness profiling |
71bfa161 JA |
13 | |
14 | 1.0 Overview and history | |
15 | ------------------------ | |
16 | fio was originally written to save me the hassle of writing special test | |
17 | case programs when I wanted to test a specific workload, either for | |
18 | performance reasons or to find/reproduce a bug. The process of writing | |
19 | such a test app can be tiresome, especially if you have to do it often. | |
20 | Hence I needed a tool that would be able to simulate a given io workload | |
21 | without resorting to writing a tailored test case again and again. | |
22 | ||
23 | A test work load is difficult to define, though. There can be any number | |
24 | of processes or threads involved, and they can each be using their own | |
25 | way of generating io. You could have someone dirtying large amounts of | |
26 | memory in an memory mapped file, or maybe several threads issuing | |
27 | reads using asynchronous io. fio needed to be flexible enough to | |
28 | simulate both of these cases, and many more. | |
29 | ||
30 | 2.0 How fio works | |
31 | ----------------- | |
32 | The first step in getting fio to simulate a desired io workload, is | |
33 | writing a job file describing that specific setup. A job file may contain | |
34 | any number of threads and/or files - the typical contents of the job file | |
35 | is a global section defining shared parameters, and one or more job | |
36 | sections describing the jobs involved. When run, fio parses this file | |
37 | and sets everything up as described. If we break down a job from top to | |
38 | bottom, it contains the following basic parameters: | |
39 | ||
40 | IO type Defines the io pattern issued to the file(s). | |
41 | We may only be reading sequentially from this | |
42 | file(s), or we may be writing randomly. Or even | |
43 | mixing reads and writes, sequentially or randomly. | |
44 | ||
45 | Block size In how large chunks are we issuing io? This may be | |
46 | a single value, or it may describe a range of | |
47 | block sizes. | |
48 | ||
49 | IO size How much data are we going to be reading/writing. | |
50 | ||
51 | IO engine How do we issue io? We could be memory mapping the | |
52 | file, we could be using regular read/write, we | |
d0ff85df | 53 | could be using splice, async io, syslet, or even |
71bfa161 JA |
54 | SG (SCSI generic sg). |
55 | ||
6c219763 | 56 | IO depth If the io engine is async, how large a queuing |
71bfa161 JA |
57 | depth do we want to maintain? |
58 | ||
59 | IO type Should we be doing buffered io, or direct/raw io? | |
60 | ||
61 | Num files How many files are we spreading the workload over. | |
62 | ||
63 | Num threads How many threads or processes should we spread | |
64 | this workload over. | |
66c098b8 | 65 | |
71bfa161 JA |
66 | The above are the basic parameters defined for a workload, in addition |
67 | there's a multitude of parameters that modify other aspects of how this | |
68 | job behaves. | |
69 | ||
70 | ||
71 | 3.0 Running fio | |
72 | --------------- | |
73 | See the README file for command line parameters, there are only a few | |
74 | of them. | |
75 | ||
76 | Running fio is normally the easiest part - you just give it the job file | |
77 | (or job files) as parameters: | |
78 | ||
79 | $ fio job_file | |
80 | ||
81 | and it will start doing what the job_file tells it to do. You can give | |
82 | more than one job file on the command line, fio will serialize the running | |
83 | of those files. Internally that is the same as using the 'stonewall' | |
84 | parameter described the the parameter section. | |
85 | ||
b4692828 JA |
86 | If the job file contains only one job, you may as well just give the |
87 | parameters on the command line. The command line parameters are identical | |
88 | to the job parameters, with a few extra that control global parameters | |
89 | (see README). For example, for the job file parameter iodepth=2, the | |
c2b1e753 JA |
90 | mirror command line option would be --iodepth 2 or --iodepth=2. You can |
91 | also use the command line for giving more than one job entry. For each | |
92 | --name option that fio sees, it will start a new job with that name. | |
93 | Command line entries following a --name entry will apply to that job, | |
94 | until there are no more entries or a new --name entry is seen. This is | |
95 | similar to the job file options, where each option applies to the current | |
96 | job until a new [] job entry is seen. | |
b4692828 | 97 | |
71bfa161 JA |
98 | fio does not need to run as root, except if the files or devices specified |
99 | in the job section requires that. Some other options may also be restricted, | |
6c219763 | 100 | such as memory locking, io scheduler switching, and decreasing the nice value. |
71bfa161 JA |
101 | |
102 | ||
103 | 4.0 Job file format | |
104 | ------------------- | |
105 | As previously described, fio accepts one or more job files describing | |
106 | what it is supposed to do. The job file format is the classic ini file, | |
107 | where the names enclosed in [] brackets define the job name. You are free | |
108 | to use any ascii name you want, except 'global' which has special meaning. | |
109 | A global section sets defaults for the jobs described in that file. A job | |
110 | may override a global section parameter, and a job file may even have | |
111 | several global sections if so desired. A job is only affected by a global | |
65db0851 JA |
112 | section residing above it. If the first character in a line is a ';' or a |
113 | '#', the entire line is discarded as a comment. | |
71bfa161 | 114 | |
3c54bc46 | 115 | So let's look at a really simple job file that defines two processes, each |
b22989b9 | 116 | randomly reading from a 128MB file. |
71bfa161 JA |
117 | |
118 | ; -- start job file -- | |
119 | [global] | |
120 | rw=randread | |
121 | size=128m | |
122 | ||
123 | [job1] | |
124 | ||
125 | [job2] | |
126 | ||
127 | ; -- end job file -- | |
128 | ||
129 | As you can see, the job file sections themselves are empty as all the | |
130 | described parameters are shared. As no filename= option is given, fio | |
c2b1e753 JA |
131 | makes up a filename for each of the jobs as it sees fit. On the command |
132 | line, this job would look as follows: | |
133 | ||
134 | $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2 | |
135 | ||
71bfa161 | 136 | |
3c54bc46 | 137 | Let's look at an example that has a number of processes writing randomly |
71bfa161 JA |
138 | to files. |
139 | ||
140 | ; -- start job file -- | |
141 | [random-writers] | |
142 | ioengine=libaio | |
143 | iodepth=4 | |
144 | rw=randwrite | |
145 | bs=32k | |
146 | direct=0 | |
147 | size=64m | |
148 | numjobs=4 | |
149 | ||
150 | ; -- end job file -- | |
151 | ||
152 | Here we have no global section, as we only have one job defined anyway. | |
153 | We want to use async io here, with a depth of 4 for each file. We also | |
b22989b9 | 154 | increased the buffer size used to 32KB and define numjobs to 4 to |
71bfa161 | 155 | fork 4 identical jobs. The result is 4 processes each randomly writing |
b22989b9 | 156 | to their own 64MB file. Instead of using the above job file, you could |
b4692828 JA |
157 | have given the parameters on the command line. For this case, you would |
158 | specify: | |
159 | ||
160 | $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4 | |
71bfa161 | 161 | |
74929ac2 JA |
162 | 4.1 Environment variables |
163 | ------------------------- | |
164 | ||
3c54bc46 AC |
165 | fio also supports environment variable expansion in job files. Any |
166 | substring of the form "${VARNAME}" as part of an option value (in other | |
167 | words, on the right of the `='), will be expanded to the value of the | |
168 | environment variable called VARNAME. If no such environment variable | |
169 | is defined, or VARNAME is the empty string, the empty string will be | |
170 | substituted. | |
171 | ||
172 | As an example, let's look at a sample fio invocation and job file: | |
173 | ||
174 | $ SIZE=64m NUMJOBS=4 fio jobfile.fio | |
175 | ||
176 | ; -- start job file -- | |
177 | [random-writers] | |
178 | rw=randwrite | |
179 | size=${SIZE} | |
180 | numjobs=${NUMJOBS} | |
181 | ; -- end job file -- | |
182 | ||
183 | This will expand to the following equivalent job file at runtime: | |
184 | ||
185 | ; -- start job file -- | |
186 | [random-writers] | |
187 | rw=randwrite | |
188 | size=64m | |
189 | numjobs=4 | |
190 | ; -- end job file -- | |
191 | ||
71bfa161 JA |
192 | fio ships with a few example job files, you can also look there for |
193 | inspiration. | |
194 | ||
74929ac2 JA |
195 | 4.2 Reserved keywords |
196 | --------------------- | |
197 | ||
198 | Additionally, fio has a set of reserved keywords that will be replaced | |
199 | internally with the appropriate value. Those keywords are: | |
200 | ||
201 | $pagesize The architecture page size of the running system | |
202 | $mb_memory Megabytes of total memory in the system | |
203 | $ncpus Number of online available CPUs | |
204 | ||
205 | These can be used on the command line or in the job file, and will be | |
206 | automatically substituted with the current system values when the job | |
892a6ffc JA |
207 | is run. Simple math is also supported on these keywords, so you can |
208 | perform actions like: | |
209 | ||
210 | size=8*$mb_memory | |
211 | ||
212 | and get that properly expanded to 8 times the size of memory in the | |
213 | machine. | |
74929ac2 | 214 | |
71bfa161 JA |
215 | |
216 | 5.0 Detailed list of parameters | |
217 | ------------------------------- | |
218 | ||
219 | This section describes in details each parameter associated with a job. | |
220 | Some parameters take an option of a given type, such as an integer or | |
221 | a string. The following types are used: | |
222 | ||
223 | str String. This is a sequence of alpha characters. | |
b09da8fa | 224 | time Integer with possible time suffix. In seconds unless otherwise |
e417fd66 | 225 | specified, use eg 10m for 10 minutes. Accepts s/m/h for seconds, |
0de5b26f JA |
226 | minutes, and hours, and accepts 'ms' (or 'msec') for milliseconds, |
227 | and 'us' (or 'usec') for microseconds. | |
b09da8fa JA |
228 | int SI integer. A whole number value, which may contain a suffix |
229 | describing the base of the number. Accepted suffixes are k/m/g/t/p, | |
230 | meaning kilo, mega, giga, tera, and peta. The suffix is not case | |
57fc29fa JA |
231 | sensitive, and you may also include trailing 'b' (eg 'kb' is the same |
232 | as 'k'). So if you want to specify 4096, you could either write | |
b09da8fa | 233 | out '4096' or just give 4k. The suffixes signify base 2 values, so |
57fc29fa JA |
234 | 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly |
235 | set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the | |
236 | case, then 1000 is used as the multiplier. This can be handy for | |
237 | disks, since manufacturers generally use base 10 values when listing | |
238 | the capacity of a drive. If the option accepts an upper and lower | |
239 | range, use a colon ':' or minus '-' to separate such values. May also | |
240 | include a prefix to indicate numbers base. If 0x is used, the number | |
241 | is assumed to be hexadecimal. See irange. | |
71bfa161 JA |
242 | bool Boolean. Usually parsed as an integer, however only defined for |
243 | true and false (1 and 0). | |
b09da8fa | 244 | irange Integer range with suffix. Allows value range to be given, such |
bf9a3edb | 245 | as 1024-4096. A colon may also be used as the separator, eg |
0c9baf91 JA |
246 | 1k:4k. If the option allows two sets of ranges, they can be |
247 | specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see | |
f7fa2653 | 248 | int. |
83349190 | 249 | float_list A list of floating numbers, separated by a ':' character. |
71bfa161 JA |
250 | |
251 | With the above in mind, here follows the complete list of fio job | |
252 | parameters. | |
253 | ||
254 | name=str ASCII name of the job. This may be used to override the | |
255 | name printed by fio for this job. Otherwise the job | |
c2b1e753 | 256 | name is used. On the command line this parameter has the |
6c219763 | 257 | special purpose of also signaling the start of a new |
c2b1e753 | 258 | job. |
71bfa161 | 259 | |
61697c37 JA |
260 | description=str Text description of the job. Doesn't do anything except |
261 | dump this text description when this job is run. It's | |
262 | not parsed. | |
263 | ||
3776041e | 264 | directory=str Prefix filenames with this directory. Used to place files |
67445b63 JA |
265 | in a different location than "./". See the 'filename' option |
266 | for escaping certain characters. | |
71bfa161 JA |
267 | |
268 | filename=str Fio normally makes up a filename based on the job name, | |
269 | thread number, and file number. If you want to share | |
270 | files between threads in a job or several jobs, specify | |
ed92ac0c | 271 | a filename for each of them to override the default. If |
414c2a3e | 272 | the ioengine used is 'net', the filename is the host, port, |
0fd666bf | 273 | and protocol to use in the format of =host,port,protocol. |
414c2a3e JA |
274 | See ioengine=net for more. If the ioengine is file based, you |
275 | can specify a number of files by separating the names with a | |
276 | ':' colon. So if you wanted a job to open /dev/sda and /dev/sdb | |
277 | as the two working files, you would use | |
30a4588a JA |
278 | filename=/dev/sda:/dev/sdb. On Windows, disk devices are |
279 | accessed as \\.\PhysicalDrive0 for the first device, | |
280 | \\.\PhysicalDrive1 for the second etc. Note: Windows and | |
281 | FreeBSD prevent write access to areas of the disk containing | |
282 | in-use data (e.g. filesystems). | |
283 | If the wanted filename does need to include a colon, then | |
284 | escape that with a '\' character. For instance, if the filename | |
285 | is "/dev/dsk/foo@3,0:c", then you would use | |
286 | filename="/dev/dsk/foo@3,0\:c". '-' is a reserved name, meaning | |
287 | stdin or stdout. Which of the two depends on the read/write | |
288 | direction set. | |
71bfa161 | 289 | |
de98bd30 JA |
290 | filename_format=str |
291 | If sharing multiple files between jobs, it is usually necessary | |
292 | to have fio generate the exact names that you want. By default, | |
293 | fio will name a file based on the default file format | |
294 | specification of jobname.jobnumber.filenumber. With this | |
295 | option, that can be customized. Fio will recognize and replace | |
296 | the following keywords in this string: | |
297 | ||
298 | $jobname | |
299 | The name of the worker thread or process. | |
300 | ||
301 | $jobnum | |
302 | The incremental number of the worker thread or | |
303 | process. | |
304 | ||
305 | $filenum | |
306 | The incremental number of the file for that worker | |
307 | thread or process. | |
308 | ||
309 | To have dependent jobs share a set of files, this option can | |
310 | be set to have fio generate filenames that are shared between | |
311 | the two. For instance, if testfiles.$filenum is specified, | |
312 | file number 4 for any job will be named testfiles.4. The | |
313 | default of $jobname.$jobnum.$filenum will be used if | |
314 | no other format specifier is given. | |
315 | ||
bbf6b540 JA |
316 | opendir=str Tell fio to recursively add any file it can find in this |
317 | directory and down the file system tree. | |
318 | ||
3776041e | 319 | lockfile=str Fio defaults to not locking any files before it does |
4d4e80f2 JA |
320 | IO to them. If a file or file descriptor is shared, fio |
321 | can serialize IO to that file to make the end result | |
322 | consistent. This is usual for emulating real workloads that | |
323 | share files. The lock modes are: | |
324 | ||
325 | none No locking. The default. | |
326 | exclusive Only one thread/process may do IO, | |
327 | excluding all others. | |
328 | readwrite Read-write locking on the file. Many | |
329 | readers may access the file at the | |
330 | same time, but writes get exclusive | |
331 | access. | |
332 | ||
d3aad8f2 | 333 | readwrite=str |
71bfa161 JA |
334 | rw=str Type of io pattern. Accepted values are: |
335 | ||
336 | read Sequential reads | |
337 | write Sequential writes | |
338 | randwrite Random writes | |
339 | randread Random reads | |
10b023db | 340 | rw,readwrite Sequential mixed reads and writes |
71bfa161 JA |
341 | randrw Random mixed reads and writes |
342 | ||
343 | For the mixed io types, the default is to split them 50/50. | |
344 | For certain types of io the result may still be skewed a bit, | |
211097b2 | 345 | since the speed may be different. It is possible to specify |
38dad62d JA |
346 | a number of IO's to do before getting a new offset, this is |
347 | one by appending a ':<nr>' to the end of the string given. | |
348 | For a random read, it would look like 'rw=randread:8' for | |
059b0802 | 349 | passing in an offset modifier with a value of 8. If the |
ddb754db | 350 | suffix is used with a sequential IO pattern, then the value |
059b0802 JA |
351 | specified will be added to the generated offset for each IO. |
352 | For instance, using rw=write:4k will skip 4k for every | |
353 | write. It turns sequential IO into sequential IO with holes. | |
354 | See the 'rw_sequencer' option. | |
38dad62d JA |
355 | |
356 | rw_sequencer=str If an offset modifier is given by appending a number to | |
357 | the rw=<str> line, then this option controls how that | |
358 | number modifies the IO offset being generated. Accepted | |
359 | values are: | |
360 | ||
361 | sequential Generate sequential offset | |
362 | identical Generate the same offset | |
363 | ||
364 | 'sequential' is only useful for random IO, where fio would | |
365 | normally generate a new random offset for every IO. If you | |
366 | append eg 8 to randread, you would get a new random offset for | |
211097b2 JA |
367 | every 8 IO's. The result would be a seek for only every 8 |
368 | IO's, instead of for every IO. Use rw=randread:8 to specify | |
38dad62d JA |
369 | that. As sequential IO is already sequential, setting |
370 | 'sequential' for that would not result in any differences. | |
371 | 'identical' behaves in a similar fashion, except it sends | |
372 | the same offset 8 number of times before generating a new | |
373 | offset. | |
71bfa161 | 374 | |
90fef2d1 JA |
375 | kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024. |
376 | Storage manufacturers like to use 10^3 or 1000 as a base | |
377 | ten unit instead, for obvious reasons. Allow values are | |
378 | 1024 or 1000, with 1024 being the default. | |
379 | ||
771e58be JA |
380 | unified_rw_reporting=bool Fio normally reports statistics on a per |
381 | data direction basis, meaning that read, write, and trim are | |
382 | accounted and reported separately. If this option is set, | |
383 | the fio will sum the results and report them as "mixed" | |
384 | instead. | |
385 | ||
ee738499 JA |
386 | randrepeat=bool For random IO workloads, seed the generator in a predictable |
387 | way so that results are repeatable across repetitions. | |
388 | ||
04778baf JA |
389 | randseed=int Seed the random number generators based on this seed value, to |
390 | be able to control what sequence of output is being generated. | |
391 | If not set, the random sequence depends on the randrepeat | |
392 | setting. | |
393 | ||
2615cc4b JA |
394 | use_os_rand=bool Fio can either use the random generator supplied by the OS |
395 | to generator random offsets, or it can use it's own internal | |
396 | generator (based on Tausworthe). Default is to use the | |
397 | internal generator, which is often of better quality and | |
398 | faster. | |
399 | ||
a596f047 EG |
400 | fallocate=str Whether pre-allocation is performed when laying down files. |
401 | Accepted values are: | |
402 | ||
403 | none Do not pre-allocate space | |
404 | posix Pre-allocate via posix_fallocate() | |
405 | keep Pre-allocate via fallocate() with | |
406 | FALLOC_FL_KEEP_SIZE set | |
407 | 0 Backward-compatible alias for 'none' | |
408 | 1 Backward-compatible alias for 'posix' | |
409 | ||
410 | May not be available on all supported platforms. 'keep' is only | |
411 | available on Linux.If using ZFS on Solaris this must be set to | |
412 | 'none' because ZFS doesn't support it. Default: 'posix'. | |
7bc8c2cf | 413 | |
d2f3ac35 JA |
414 | fadvise_hint=bool By default, fio will use fadvise() to advise the kernel |
415 | on what IO patterns it is likely to issue. Sometimes you | |
416 | want to test specific IO patterns without telling the | |
417 | kernel about it, in which case you can disable this option. | |
418 | If set, fio will use POSIX_FADV_SEQUENTIAL for sequential | |
419 | IO and POSIX_FADV_RANDOM for random IO. | |
420 | ||
f7fa2653 | 421 | size=int The total size of file io for this job. Fio will run until |
7616cafe JA |
422 | this many bytes has been transferred, unless runtime is |
423 | limited by other options (such as 'runtime', for instance). | |
3776041e | 424 | Unless specific nrfiles and filesize options are given, |
7616cafe | 425 | fio will divide this size between the available files |
d6667268 JA |
426 | specified by the job. If not set, fio will use the full |
427 | size of the given files or devices. If the the files | |
7bb59102 JA |
428 | do not exist, size must be given. It is also possible to |
429 | give size as a percentage between 1 and 100. If size=20% | |
430 | is given, fio will use 20% of the full size of the given | |
431 | files or devices. | |
71bfa161 | 432 | |
f7fa2653 | 433 | filesize=int Individual file sizes. May be a range, in which case fio |
9c60ce64 JA |
434 | will select sizes for files at random within the given range |
435 | and limited to 'size' in total (if that is given). If not | |
436 | given, each created file is the same size. | |
437 | ||
bedc9dc2 JA |
438 | file_append=bool Perform IO after the end of the file. Normally fio will |
439 | operate within the size of a file. If this option is set, then | |
440 | fio will append to the file instead. This has identical | |
0aae4ce7 JA |
441 | behavior to setting offset to the size of a file. This option |
442 | is ignored on non-regular files. | |
bedc9dc2 | 443 | |
74586c1e JA |
444 | fill_device=bool |
445 | fill_fs=bool Sets size to something really large and waits for ENOSPC (no | |
aa31f1f1 | 446 | space left on device) as the terminating condition. Only makes |
de98bd30 | 447 | sense with sequential write. For a read workload, the mount |
4f12432e JA |
448 | point will be filled first then IO started on the result. This |
449 | option doesn't make sense if operating on a raw device node, | |
450 | since the size of that is already known by the file system. | |
451 | Additionally, writing beyond end-of-device will not return | |
452 | ENOSPC there. | |
aa31f1f1 | 453 | |
f7fa2653 JA |
454 | blocksize=int |
455 | bs=int The block size used for the io units. Defaults to 4k. Values | |
456 | can be given for both read and writes. If a single int is | |
457 | given, it will apply to both. If a second int is specified | |
f90eff5a | 458 | after a comma, it will apply to writes only. In other words, |
d9472271 JA |
459 | the format is either bs=read_and_write or bs=read,write,trim. |
460 | bs=4k,8k will thus use 4k blocks for reads, 8k blocks for | |
461 | writes, and 8k for trims. You can terminate the list with | |
462 | a trailing comma. bs=4k,8k, would use the default value for | |
463 | trims.. If you only wish to set the write size, you | |
787f7e95 JA |
464 | can do so by passing an empty read size - bs=,8k will set |
465 | 8k for writes and leave the read default value. | |
a00735e6 | 466 | |
2b7a01d0 JA |
467 | blockalign=int |
468 | ba=int At what boundary to align random IO offsets. Defaults to | |
469 | the same as 'blocksize' the minimum blocksize given. | |
470 | Minimum alignment is typically 512b for using direct IO, | |
471 | though it usually depends on the hardware block size. This | |
472 | option is mutually exclusive with using a random map for | |
473 | files, so it will turn off that option. | |
474 | ||
d3aad8f2 | 475 | blocksize_range=irange |
71bfa161 JA |
476 | bsrange=irange Instead of giving a single block size, specify a range |
477 | and fio will mix the issued io block sizes. The issued | |
478 | io unit will always be a multiple of the minimum value | |
f90eff5a JA |
479 | given (also see bs_unaligned). Applies to both reads and |
480 | writes, however a second range can be given after a comma. | |
481 | See bs=. | |
a00735e6 | 482 | |
564ca972 JA |
483 | bssplit=str Sometimes you want even finer grained control of the |
484 | block sizes issued, not just an even split between them. | |
485 | This option allows you to weight various block sizes, | |
486 | so that you are able to define a specific amount of | |
487 | block sizes issued. The format for this option is: | |
488 | ||
489 | bssplit=blocksize/percentage:blocksize/percentage | |
490 | ||
491 | for as many block sizes as needed. So if you want to define | |
492 | a workload that has 50% 64k blocks, 10% 4k blocks, and | |
493 | 40% 32k blocks, you would write: | |
494 | ||
495 | bssplit=4k/10:64k/50:32k/40 | |
496 | ||
497 | Ordering does not matter. If the percentage is left blank, | |
498 | fio will fill in the remaining values evenly. So a bssplit | |
499 | option like this one: | |
500 | ||
501 | bssplit=4k/50:1k/:32k/ | |
502 | ||
503 | would have 50% 4k ios, and 25% 1k and 32k ios. The percentages | |
504 | always add up to 100, if bssplit is given a range that adds | |
505 | up to more, it will error out. | |
506 | ||
720e84ad JA |
507 | bssplit also supports giving separate splits to reads and |
508 | writes. The format is identical to what bs= accepts. You | |
509 | have to separate the read and write parts with a comma. So | |
510 | if you want a workload that has 50% 2k reads and 50% 4k reads, | |
511 | while having 90% 4k writes and 10% 8k writes, you would | |
512 | specify: | |
513 | ||
514 | bssplit=2k/50:4k/50,4k/90,8k/10 | |
515 | ||
d3aad8f2 | 516 | blocksize_unaligned |
690adba3 JA |
517 | bs_unaligned If this option is given, any byte size value within bsrange |
518 | may be used as a block range. This typically wont work with | |
519 | direct IO, as that normally requires sector alignment. | |
71bfa161 | 520 | |
6aca9b3d JA |
521 | bs_is_seq_rand If this option is set, fio will use the normal read,write |
522 | blocksize settings as sequential,random instead. Any random | |
523 | read or write will use the WRITE blocksize settings, and any | |
524 | sequential read or write will use the READ blocksize setting. | |
525 | ||
e9459e5a JA |
526 | zero_buffers If this option is given, fio will init the IO buffers to |
527 | all zeroes. The default is to fill them with random data. | |
7750aac4 JA |
528 | The resulting IO buffers will not be completely zeroed, |
529 | unless scramble_buffers is also turned off. | |
e9459e5a | 530 | |
5973cafb JA |
531 | refill_buffers If this option is given, fio will refill the IO buffers |
532 | on every submit. The default is to only fill it at init | |
533 | time and reuse that data. Only makes sense if zero_buffers | |
41ccd845 JA |
534 | isn't specified, naturally. If data verification is enabled, |
535 | refill_buffers is also automatically enabled. | |
5973cafb | 536 | |
fd68418e JA |
537 | scramble_buffers=bool If refill_buffers is too costly and the target is |
538 | using data deduplication, then setting this option will | |
539 | slightly modify the IO buffer contents to defeat normal | |
540 | de-dupe attempts. This is not enough to defeat more clever | |
541 | block compression attempts, but it will stop naive dedupe of | |
542 | blocks. Default: true. | |
543 | ||
c5751c62 JA |
544 | buffer_compress_percentage=int If this is set, then fio will attempt to |
545 | provide IO buffer content (on WRITEs) that compress to | |
546 | the specified level. Fio does this by providing a mix of | |
547 | random data and zeroes. Note that this is per block size | |
548 | unit, for file/disk wide compression level that matches | |
549 | this setting, you'll also want to set refill_buffers. | |
550 | ||
551 | buffer_compress_chunk=int See buffer_compress_percentage. This | |
552 | setting allows fio to manage how big the ranges of random | |
553 | data and zeroed data is. Without this set, fio will | |
554 | provide buffer_compress_percentage of blocksize random | |
555 | data, followed by the remaining zeroed. With this set | |
556 | to some chunk size smaller than the block size, fio can | |
557 | alternate random and zeroed data throughout the IO | |
558 | buffer. | |
559 | ||
ce35b1ec JA |
560 | buffer_pattern=str If set, fio will fill the io buffers with this pattern. |
561 | If not set, the contents of io buffers is defined by the other | |
562 | options related to buffer contents. The setting can be any | |
563 | pattern of bytes, and can be prefixed with 0x for hex values. | |
564 | ||
71bfa161 JA |
565 | nrfiles=int Number of files to use for this job. Defaults to 1. |
566 | ||
390b1537 JA |
567 | openfiles=int Number of files to keep open at the same time. Defaults to |
568 | the same as nrfiles, can be set smaller to limit the number | |
569 | simultaneous opens. | |
570 | ||
5af1c6f3 JA |
571 | file_service_type=str Defines how fio decides which file from a job to |
572 | service next. The following types are defined: | |
573 | ||
574 | random Just choose a file at random. | |
575 | ||
576 | roundrobin Round robin over open files. This | |
577 | is the default. | |
578 | ||
a086c257 JA |
579 | sequential Finish one file before moving on to |
580 | the next. Multiple files can still be | |
581 | open depending on 'openfiles'. | |
582 | ||
1907dbc6 JA |
583 | The string can have a number appended, indicating how |
584 | often to switch to a new file. So if option random:4 is | |
585 | given, fio will switch to a new random file after 4 ios | |
586 | have been issued. | |
587 | ||
71bfa161 JA |
588 | ioengine=str Defines how the job issues io to the file. The following |
589 | types are defined: | |
590 | ||
591 | sync Basic read(2) or write(2) io. lseek(2) is | |
592 | used to position the io location. | |
593 | ||
a31041ea | 594 | psync Basic pread(2) or pwrite(2) io. |
595 | ||
e05af9e5 | 596 | vsync Basic readv(2) or writev(2) IO. |
1d2af02a | 597 | |
a46c5e01 JA |
598 | psyncv Basic preadv(2) or pwritev(2) IO. |
599 | ||
15d182aa JA |
600 | libaio Linux native asynchronous io. Note that Linux |
601 | may only support queued behaviour with | |
602 | non-buffered IO (set direct=1 or buffered=0). | |
de890a1e | 603 | This engine defines engine specific options. |
71bfa161 JA |
604 | |
605 | posixaio glibc posix asynchronous io. | |
606 | ||
417f0068 JA |
607 | solarisaio Solaris native asynchronous io. |
608 | ||
03e20d68 BC |
609 | windowsaio Windows native asynchronous io. |
610 | ||
71bfa161 JA |
611 | mmap File is memory mapped and data copied |
612 | to/from using memcpy(3). | |
613 | ||
614 | splice splice(2) is used to transfer the data and | |
615 | vmsplice(2) to transfer data from user | |
616 | space to the kernel. | |
617 | ||
d0ff85df JA |
618 | syslet-rw Use the syslet system calls to make |
619 | regular read/write async. | |
620 | ||
71bfa161 | 621 | sg SCSI generic sg v3 io. May either be |
6c219763 | 622 | synchronous using the SG_IO ioctl, or if |
71bfa161 JA |
623 | the target is an sg character device |
624 | we use read(2) and write(2) for asynchronous | |
625 | io. | |
626 | ||
a94ea28b JA |
627 | null Doesn't transfer any data, just pretends |
628 | to. This is mainly used to exercise fio | |
629 | itself and for debugging/testing purposes. | |
630 | ||
ed92ac0c | 631 | net Transfer over the network to given host:port. |
de890a1e SL |
632 | Depending on the protocol used, the hostname, |
633 | port, listen and filename options are used to | |
634 | specify what sort of connection to make, while | |
635 | the protocol option determines which protocol | |
636 | will be used. | |
637 | This engine defines engine specific options. | |
ed92ac0c | 638 | |
9cce02e8 JA |
639 | netsplice Like net, but uses splice/vmsplice to |
640 | map data and send/receive. | |
de890a1e | 641 | This engine defines engine specific options. |
9cce02e8 | 642 | |
53aec0a4 | 643 | cpuio Doesn't transfer any data, but burns CPU |
ba0fbe10 JA |
644 | cycles according to the cpuload= and |
645 | cpucycle= options. Setting cpuload=85 | |
646 | will cause that job to do nothing but burn | |
36ecec83 GP |
647 | 85% of the CPU. In case of SMP machines, |
648 | use numjobs=<no_of_cpu> to get desired CPU | |
649 | usage, as the cpuload only loads a single | |
650 | CPU at the desired rate. | |
ba0fbe10 | 651 | |
e9a1806f JA |
652 | guasi The GUASI IO engine is the Generic Userspace |
653 | Asyncronous Syscall Interface approach | |
654 | to async IO. See | |
655 | ||
656 | http://www.xmailserver.org/guasi-lib.html | |
657 | ||
658 | for more info on GUASI. | |
659 | ||
21b8aee8 | 660 | rdma The RDMA I/O engine supports both RDMA |
eb52fa3f BVA |
661 | memory semantics (RDMA_WRITE/RDMA_READ) and |
662 | channel semantics (Send/Recv) for the | |
663 | InfiniBand, RoCE and iWARP protocols. | |
21b8aee8 | 664 | |
d54fce84 DM |
665 | falloc IO engine that does regular fallocate to |
666 | simulate data transfer as fio ioengine. | |
667 | DDIR_READ does fallocate(,mode = keep_size,) | |
0981fd71 | 668 | DDIR_WRITE does fallocate(,mode = 0) |
d54fce84 DM |
669 | DDIR_TRIM does fallocate(,mode = punch_hole) |
670 | ||
671 | e4defrag IO engine that does regular EXT4_IOC_MOVE_EXT | |
672 | ioctls to simulate defragment activity in | |
673 | request to DDIR_WRITE event | |
0981fd71 | 674 | |
8a7bd877 JA |
675 | external Prefix to specify loading an external |
676 | IO engine object file. Append the engine | |
677 | filename, eg ioengine=external:/tmp/foo.o | |
678 | to load ioengine foo.o in /tmp. | |
679 | ||
71bfa161 JA |
680 | iodepth=int This defines how many io units to keep in flight against |
681 | the file. The default is 1 for each file defined in this | |
682 | job, can be overridden with a larger value for higher | |
ee72ca09 JA |
683 | concurrency. Note that increasing iodepth beyond 1 will not |
684 | affect synchronous ioengines (except for small degress when | |
9b836561 | 685 | verify_async is in use). Even async engines may impose OS |
ee72ca09 JA |
686 | restrictions causing the desired depth not to be achieved. |
687 | This may happen on Linux when using libaio and not setting | |
688 | direct=1, since buffered IO is not async on that OS. Keep an | |
689 | eye on the IO depth distribution in the fio output to verify | |
690 | that the achieved depth is as expected. Default: 1. | |
71bfa161 | 691 | |
4950421a | 692 | iodepth_batch_submit=int |
cb5ab512 | 693 | iodepth_batch=int This defines how many pieces of IO to submit at once. |
89e820f6 JA |
694 | It defaults to 1 which means that we submit each IO |
695 | as soon as it is available, but can be raised to submit | |
696 | bigger batches of IO at the time. | |
cb5ab512 | 697 | |
4950421a JA |
698 | iodepth_batch_complete=int This defines how many pieces of IO to retrieve |
699 | at once. It defaults to 1 which means that we'll ask | |
700 | for a minimum of 1 IO in the retrieval process from | |
701 | the kernel. The IO retrieval will go on until we | |
702 | hit the limit set by iodepth_low. If this variable is | |
703 | set to 0, then fio will always check for completed | |
704 | events before queuing more IO. This helps reduce | |
705 | IO latency, at the cost of more retrieval system calls. | |
706 | ||
e916b390 JA |
707 | iodepth_low=int The low water mark indicating when to start filling |
708 | the queue again. Defaults to the same as iodepth, meaning | |
709 | that fio will attempt to keep the queue full at all times. | |
710 | If iodepth is set to eg 16 and iodepth_low is set to 4, then | |
711 | after fio has filled the queue of 16 requests, it will let | |
712 | the depth drain down to 4 before starting to fill it again. | |
713 | ||
71bfa161 | 714 | direct=bool If value is true, use non-buffered io. This is usually |
9b836561 | 715 | O_DIRECT. Note that ZFS on Solaris doesn't support direct io. |
93bcfd20 | 716 | On Windows the synchronous ioengines don't support direct io. |
76a43db4 | 717 | |
d01612f3 CM |
718 | atomic=bool If value is true, attempt to use atomic direct IO. Atomic |
719 | writes are guaranteed to be stable once acknowledged by | |
720 | the operating system. Only Linux supports O_ATOMIC right | |
721 | now. | |
722 | ||
76a43db4 JA |
723 | buffered=bool If value is true, use buffered io. This is the opposite |
724 | of the 'direct' option. Defaults to true. | |
71bfa161 | 725 | |
f7fa2653 | 726 | offset=int Start io at the given offset in the file. The data before |
71bfa161 JA |
727 | the given offset will not be touched. This effectively |
728 | caps the file size at real_size - offset. | |
729 | ||
214ac7e0 DE |
730 | offset_increment=int If this is provided, then the real offset becomes |
731 | the offset + offset_increment * thread_number, where the | |
732 | thread number is a counter that starts at 0 and is incremented | |
733 | for each job. This option is useful if there are several jobs | |
734 | which are intended to operate on a file in parallel in disjoint | |
735 | segments, with even spacing between the starting points. | |
736 | ||
ddf24e42 JA |
737 | number_ios=int Fio will normally perform IOs until it has exhausted the size |
738 | of the region set by size=, or if it exhaust the allocated | |
739 | time (or hits an error condition). With this setting, the | |
740 | range/size can be set independently of the number of IOs to | |
741 | perform. When fio reaches this number, it will exit normally | |
742 | and report status. | |
743 | ||
71bfa161 JA |
744 | fsync=int If writing to a file, issue a sync of the dirty data |
745 | for every number of blocks given. For example, if you give | |
746 | 32 as a parameter, fio will sync the file for every 32 | |
747 | writes issued. If fio is using non-buffered io, we may | |
748 | not sync the file. The exception is the sg io engine, which | |
6c219763 | 749 | synchronizes the disk cache anyway. |
71bfa161 | 750 | |
e76b1da4 | 751 | fdatasync=int Like fsync= but uses fdatasync() to only sync data and not |
5f9099ea | 752 | metadata blocks. |
93bcfd20 | 753 | In FreeBSD and Windows there is no fdatasync(), this falls back to |
e72fa4d4 | 754 | using fsync() |
5f9099ea | 755 | |
e76b1da4 JA |
756 | sync_file_range=str:val Use sync_file_range() for every 'val' number of |
757 | write operations. Fio will track range of writes that | |
758 | have happened since the last sync_file_range() call. 'str' | |
759 | can currently be one or more of: | |
760 | ||
761 | wait_before SYNC_FILE_RANGE_WAIT_BEFORE | |
762 | write SYNC_FILE_RANGE_WRITE | |
763 | wait_after SYNC_FILE_RANGE_WAIT_AFTER | |
764 | ||
765 | So if you do sync_file_range=wait_before,write:8, fio would | |
766 | use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for | |
767 | every 8 writes. Also see the sync_file_range(2) man page. | |
768 | This option is Linux specific. | |
769 | ||
5036fc1e JA |
770 | overwrite=bool If true, writes to a file will always overwrite existing |
771 | data. If the file doesn't already exist, it will be | |
772 | created before the write phase begins. If the file exists | |
773 | and is large enough for the specified write phase, nothing | |
774 | will be done. | |
71bfa161 | 775 | |
dbd11ead | 776 | end_fsync=bool If true, fsync file contents when a write stage has completed. |
71bfa161 | 777 | |
ebb1415f JA |
778 | fsync_on_close=bool If true, fio will fsync() a dirty file on close. |
779 | This differs from end_fsync in that it will happen on every | |
780 | file close, not just at the end of the job. | |
781 | ||
71bfa161 JA |
782 | rwmixread=int How large a percentage of the mix should be reads. |
783 | ||
784 | rwmixwrite=int How large a percentage of the mix should be writes. If both | |
785 | rwmixread and rwmixwrite is given and the values do not add | |
786 | up to 100%, the latter of the two will be used to override | |
c35dd7a6 JA |
787 | the first. This may interfere with a given rate setting, |
788 | if fio is asked to limit reads or writes to a certain rate. | |
789 | If that is the case, then the distribution may be skewed. | |
71bfa161 | 790 | |
92d42d69 JA |
791 | random_distribution=str:float By default, fio will use a completely uniform |
792 | random distribution when asked to perform random IO. Sometimes | |
793 | it is useful to skew the distribution in specific ways, | |
794 | ensuring that some parts of the data is more hot than others. | |
795 | fio includes the following distribution models: | |
796 | ||
797 | random Uniform random distribution | |
798 | zipf Zipf distribution | |
799 | pareto Pareto distribution | |
800 | ||
801 | When using a zipf or pareto distribution, an input value | |
802 | is also needed to define the access pattern. For zipf, this | |
803 | is the zipf theta. For pareto, it's the pareto power. Fio | |
804 | includes a test program, genzipf, that can be used visualize | |
805 | what the given input values will yield in terms of hit rates. | |
806 | If you wanted to use zipf with a theta of 1.2, you would use | |
807 | random_distribution=zipf:1.2 as the option. If a non-uniform | |
808 | model is used, fio will disable use of the random map. | |
809 | ||
211c9b89 JA |
810 | percentage_random=int For a random workload, set how big a percentage should |
811 | be random. This defaults to 100%, in which case the workload | |
812 | is fully random. It can be set from anywhere from 0 to 100. | |
813 | Setting it to 0 would make the workload fully sequential. Any | |
814 | setting in between will result in a random mix of sequential | |
d9472271 JA |
815 | and random IO, at the given percentages. It is possible to |
816 | set different values for reads, writes, and trim. To do so, | |
817 | simply use a comma separated list. See blocksize. | |
211c9b89 | 818 | |
bb8895e0 JA |
819 | norandommap Normally fio will cover every block of the file when doing |
820 | random IO. If this option is given, fio will just get a | |
821 | new random offset without looking at past io history. This | |
822 | means that some blocks may not be read or written, and that | |
823 | some blocks may be read/written more than once. This option | |
8347239a JA |
824 | is mutually exclusive with verify= if and only if multiple |
825 | blocksizes (via bsrange=) are used, since fio only tracks | |
826 | complete rewrites of blocks. | |
bb8895e0 | 827 | |
0408c206 JA |
828 | softrandommap=bool See norandommap. If fio runs with the random block map |
829 | enabled and it fails to allocate the map, if this option is | |
830 | set it will continue without a random block map. As coverage | |
831 | will not be as complete as with random maps, this option is | |
2b386d25 JA |
832 | disabled by default. |
833 | ||
e8b1961d JA |
834 | random_generator=str Fio supports the following engines for generating |
835 | IO offsets for random IO: | |
836 | ||
837 | tausworthe Strong 2^88 cycle random number generator | |
838 | lfsr Linear feedback shift register generator | |
839 | ||
840 | Tausworthe is a strong random number generator, but it | |
841 | requires tracking on the side if we want to ensure that | |
842 | blocks are only read or written once. LFSR guarantees | |
843 | that we never generate the same offset twice, and it's | |
844 | also less computationally expensive. It's not a true | |
845 | random generator, however, though for IO purposes it's | |
846 | typically good enough. LFSR only works with single | |
847 | block sizes, not with workloads that use multiple block | |
848 | sizes. If used with such a workload, fio may read or write | |
849 | some blocks multiple times. | |
43f09da1 | 850 | |
71bfa161 JA |
851 | nice=int Run the job with the given nice value. See man nice(2). |
852 | ||
853 | prio=int Set the io priority value of this job. Linux limits us to | |
854 | a positive value between 0 and 7, with 0 being the highest. | |
855 | See man ionice(1). | |
856 | ||
857 | prioclass=int Set the io priority class. See man ionice(1). | |
858 | ||
859 | thinktime=int Stall the job x microseconds after an io has completed before | |
860 | issuing the next. May be used to simulate processing being | |
48097d5c JA |
861 | done by an application. See thinktime_blocks and |
862 | thinktime_spin. | |
863 | ||
864 | thinktime_spin=int | |
865 | Only valid if thinktime is set - pretend to spend CPU time | |
866 | doing something with the data received, before falling back | |
867 | to sleeping for the rest of the period specified by | |
868 | thinktime. | |
9c1f7434 | 869 | |
4d01ece6 | 870 | thinktime_blocks=int |
9c1f7434 JA |
871 | Only valid if thinktime is set - control how many blocks |
872 | to issue, before waiting 'thinktime' usecs. If not set, | |
873 | defaults to 1 which will make fio wait 'thinktime' usecs | |
4d01ece6 JA |
874 | after every block. This effectively makes any queue depth |
875 | setting redundant, since no more than 1 IO will be queued | |
876 | before we have to complete it and do our thinktime. In | |
877 | other words, this setting effectively caps the queue depth | |
878 | if the latter is larger. | |
71bfa161 | 879 | |
581e7141 | 880 | rate=int Cap the bandwidth used by this job. The number is in bytes/sec, |
b09da8fa | 881 | the normal suffix rules apply. You can use rate=500k to limit |
581e7141 JA |
882 | reads and writes to 500k each, or you can specify read and |
883 | writes separately. Using rate=1m,500k would limit reads to | |
884 | 1MB/sec and writes to 500KB/sec. Capping only reads or | |
885 | writes can be done with rate=,500k or rate=500k,. The former | |
886 | will only limit writes (to 500KB/sec), the latter will only | |
887 | limit reads. | |
71bfa161 JA |
888 | |
889 | ratemin=int Tell fio to do whatever it can to maintain at least this | |
4e991c23 | 890 | bandwidth. Failing to meet this requirement, will cause |
581e7141 JA |
891 | the job to exit. The same format as rate is used for |
892 | read vs write separation. | |
4e991c23 JA |
893 | |
894 | rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same | |
895 | as rate, just specified independently of bandwidth. If the | |
896 | job is given a block size range instead of a fixed value, | |
581e7141 | 897 | the smallest block size is used as the metric. The same format |
de8f6de9 | 898 | as rate is used for read vs write separation. |
4e991c23 JA |
899 | |
900 | rate_iops_min=int If fio doesn't meet this rate of IO, it will cause | |
581e7141 | 901 | the job to exit. The same format as rate is used for read vs |
de8f6de9 | 902 | write separation. |
71bfa161 | 903 | |
3e260a46 JA |
904 | latency_target=int If set, fio will attempt to find the max performance |
905 | point that the given workload will run at while maintaining a | |
906 | latency below this target. The values is given in microseconds. | |
907 | See latency_window and latency_percentile | |
908 | ||
909 | latency_window=int Used with latency_target to specify the sample window | |
910 | that the job is run at varying queue depths to test the | |
911 | performance. The value is given in microseconds. | |
912 | ||
913 | latency_percentile=float The percentage of IOs that must fall within the | |
914 | criteria specified by latency_target and latency_window. If not | |
915 | set, this defaults to 100.0, meaning that all IOs must be equal | |
916 | or below to the value set by latency_target. | |
917 | ||
15501535 JA |
918 | max_latency=int If set, fio will exit the job if it exceeds this maximum |
919 | latency. It will exit with an ETIME error. | |
920 | ||
71bfa161 | 921 | ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number |
6c219763 | 922 | of milliseconds. |
71bfa161 JA |
923 | |
924 | cpumask=int Set the CPU affinity of this job. The parameter given is a | |
a08bc17f JA |
925 | bitmask of allowed CPU's the job may run on. So if you want |
926 | the allowed CPUs to be 1 and 5, you would pass the decimal | |
927 | value of (1 << 1 | 1 << 5), or 34. See man | |
7dbb6eba | 928 | sched_setaffinity(2). This may not work on all supported |
b0ea08ce JA |
929 | operating systems or kernel versions. This option doesn't |
930 | work well for a higher CPU count than what you can store in | |
931 | an integer mask, so it can only control cpus 1-32. For | |
932 | boxes with larger CPU counts, use cpus_allowed. | |
71bfa161 | 933 | |
d2e268b0 JA |
934 | cpus_allowed=str Controls the same options as cpumask, but it allows a text |
935 | setting of the permitted CPUs instead. So to use CPUs 1 and | |
62a7273d JA |
936 | 5, you would specify cpus_allowed=1,5. This options also |
937 | allows a range of CPUs. Say you wanted a binding to CPUs | |
938 | 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15. | |
d2e268b0 | 939 | |
c2acfbac JA |
940 | cpus_allowed_policy=str Set the policy of how fio distributes the CPUs |
941 | specified by cpus_allowed or cpumask. Two policies are | |
942 | supported: | |
943 | ||
944 | shared All jobs will share the CPU set specified. | |
945 | split Each job will get a unique CPU from the CPU set. | |
946 | ||
947 | 'shared' is the default behaviour, if the option isn't | |
ada083cd JA |
948 | specified. If split is specified, then fio will will assign |
949 | one cpu per job. If not enough CPUs are given for the jobs | |
950 | listed, then fio will roundrobin the CPUs in the set. | |
c2acfbac | 951 | |
d0b937ed YR |
952 | numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The |
953 | arguments allow comma delimited list of cpu numbers, | |
954 | A-B ranges, or 'all'. Note, to enable numa options support, | |
67bf9823 | 955 | fio must be built on a system with libnuma-dev(el) installed. |
d0b937ed YR |
956 | |
957 | numa_mem_policy=str Set this job's memory policy and corresponding NUMA | |
958 | nodes. Format of the argements: | |
959 | <mode>[:<nodelist>] | |
960 | `mode' is one of the following memory policy: | |
961 | default, prefer, bind, interleave, local | |
962 | For `default' and `local' memory policy, no node is | |
963 | needed to be specified. | |
964 | For `prefer', only one node is allowed. | |
965 | For `bind' and `interleave', it allow comma delimited | |
966 | list of numbers, A-B ranges, or 'all'. | |
967 | ||
e417fd66 | 968 | startdelay=time Start this job the specified number of seconds after fio |
71bfa161 JA |
969 | has started. Only useful if the job file contains several |
970 | jobs, and you want to delay starting some jobs to a certain | |
971 | time. | |
972 | ||
e417fd66 | 973 | runtime=time Tell fio to terminate processing after the specified number |
71bfa161 JA |
974 | of seconds. It can be quite hard to determine for how long |
975 | a specified job will run, so this parameter is handy to | |
976 | cap the total runtime to a given time. | |
977 | ||
cf4464ca | 978 | time_based If set, fio will run for the duration of the runtime |
bf9a3edb | 979 | specified even if the file(s) are completely read or |
cf4464ca JA |
980 | written. It will simply loop over the same workload |
981 | as many times as the runtime allows. | |
982 | ||
e417fd66 | 983 | ramp_time=time If set, fio will run the specified workload for this amount |
721938ae JA |
984 | of time before logging any performance numbers. Useful for |
985 | letting performance settle before logging results, thus | |
b29ee5b3 JA |
986 | minimizing the runtime required for stable results. Note |
987 | that the ramp_time is considered lead in time for a job, | |
988 | thus it will increase the total runtime if a special timeout | |
989 | or runtime is specified. | |
721938ae | 990 | |
71bfa161 JA |
991 | invalidate=bool Invalidate the buffer/page cache parts for this file prior |
992 | to starting io. Defaults to true. | |
993 | ||
994 | sync=bool Use sync io for buffered writes. For the majority of the | |
995 | io engines, this means using O_SYNC. | |
996 | ||
d3aad8f2 | 997 | iomem=str |
71bfa161 JA |
998 | mem=str Fio can use various types of memory as the io unit buffer. |
999 | The allowed values are: | |
1000 | ||
1001 | malloc Use memory from malloc(3) as the buffers. | |
1002 | ||
1003 | shm Use shared memory as the buffers. Allocated | |
1004 | through shmget(2). | |
1005 | ||
74b025b0 JA |
1006 | shmhuge Same as shm, but use huge pages as backing. |
1007 | ||
313cb206 JA |
1008 | mmap Use mmap to allocate buffers. May either be |
1009 | anonymous memory, or can be file backed if | |
1010 | a filename is given after the option. The | |
1011 | format is mem=mmap:/path/to/file. | |
71bfa161 | 1012 | |
d0bdaf49 JA |
1013 | mmaphuge Use a memory mapped huge file as the buffer |
1014 | backing. Append filename after mmaphuge, ala | |
1015 | mem=mmaphuge:/hugetlbfs/file | |
1016 | ||
71bfa161 | 1017 | The area allocated is a function of the maximum allowed |
5394ae5f JA |
1018 | bs size for the job, multiplied by the io depth given. Note |
1019 | that for shmhuge and mmaphuge to work, the system must have | |
1020 | free huge pages allocated. This can normally be checked | |
1021 | and set by reading/writing /proc/sys/vm/nr_hugepages on a | |
b22989b9 | 1022 | Linux system. Fio assumes a huge page is 4MB in size. So |
5394ae5f JA |
1023 | to calculate the number of huge pages you need for a given |
1024 | job file, add up the io depth of all jobs (normally one unless | |
1025 | iodepth= is used) and multiply by the maximum bs set. Then | |
1026 | divide that number by the huge page size. You can see the | |
1027 | size of the huge pages in /proc/meminfo. If no huge pages | |
1028 | are allocated by having a non-zero number in nr_hugepages, | |
56bb17f2 | 1029 | using mmaphuge or shmhuge will fail. Also see hugepage-size. |
5394ae5f JA |
1030 | |
1031 | mmaphuge also needs to have hugetlbfs mounted and the file | |
1032 | location should point there. So if it's mounted in /huge, | |
1033 | you would use mem=mmaphuge:/huge/somefile. | |
71bfa161 | 1034 | |
d529ee19 JA |
1035 | iomem_align=int This indiciates the memory alignment of the IO memory buffers. |
1036 | Note that the given alignment is applied to the first IO unit | |
1037 | buffer, if using iodepth the alignment of the following buffers | |
1038 | are given by the bs used. In other words, if using a bs that is | |
1039 | a multiple of the page sized in the system, all buffers will | |
1040 | be aligned to this value. If using a bs that is not page | |
1041 | aligned, the alignment of subsequent IO memory buffers is the | |
1042 | sum of the iomem_align and bs used. | |
1043 | ||
f7fa2653 | 1044 | hugepage-size=int |
56bb17f2 | 1045 | Defines the size of a huge page. Must at least be equal |
b22989b9 | 1046 | to the system setting, see /proc/meminfo. Defaults to 4MB. |
c51074e7 JA |
1047 | Should probably always be a multiple of megabytes, so using |
1048 | hugepage-size=Xm is the preferred way to set this to avoid | |
1049 | setting a non-pow-2 bad value. | |
56bb17f2 | 1050 | |
71bfa161 JA |
1051 | exitall When one job finishes, terminate the rest. The default is |
1052 | to wait for each job to finish, sometimes that is not the | |
1053 | desired action. | |
1054 | ||
1055 | bwavgtime=int Average the calculated bandwidth over the given time. Value | |
6c219763 | 1056 | is specified in milliseconds. |
71bfa161 | 1057 | |
c8eeb9df JA |
1058 | iopsavgtime=int Average the calculated IOPS over the given time. Value |
1059 | is specified in milliseconds. | |
1060 | ||
71bfa161 JA |
1061 | create_serialize=bool If true, serialize the file creating for the jobs. |
1062 | This may be handy to avoid interleaving of data | |
1063 | files, which may greatly depend on the filesystem | |
1064 | used and even the number of processors in the system. | |
1065 | ||
1066 | create_fsync=bool fsync the data file after creation. This is the | |
1067 | default. | |
1068 | ||
814452bd JA |
1069 | create_on_open=bool Don't pre-setup the files for IO, just create open() |
1070 | when it's time to do IO to that file. | |
1071 | ||
25460cf6 JA |
1072 | create_only=bool If true, fio will only run the setup phase of the job. |
1073 | If files need to be laid out or updated on disk, only | |
1074 | that will be done. The actual job contents are not | |
1075 | executed. | |
1076 | ||
afad68f7 | 1077 | pre_read=bool If this is given, files will be pre-read into memory before |
34f1c044 JA |
1078 | starting the given IO operation. This will also clear |
1079 | the 'invalidate' flag, since it is pointless to pre-read | |
9c0d2241 JA |
1080 | and then drop the cache. This will only work for IO engines |
1081 | that are seekable, since they allow you to read the same data | |
1082 | multiple times. Thus it will not work on eg network or splice | |
1083 | IO. | |
afad68f7 | 1084 | |
e545a6ce | 1085 | unlink=bool Unlink the job files when done. Not the default, as repeated |
bf9a3edb JA |
1086 | runs of that job would then waste time recreating the file |
1087 | set again and again. | |
71bfa161 JA |
1088 | |
1089 | loops=int Run the specified number of iterations of this job. Used | |
1090 | to repeat the same workload a given number of times. Defaults | |
1091 | to 1. | |
1092 | ||
62167762 JC |
1093 | verify_only Do not perform specified workload---only verify data still |
1094 | matches previous invocation of this workload. This option | |
1095 | allows one to check data multiple times at a later date | |
1096 | without overwriting it. This option makes sense only for | |
1097 | workloads that write data, and does not support workloads | |
1098 | with the time_based option set. | |
1099 | ||
68e1f29a | 1100 | do_verify=bool Run the verify phase after a write phase. Only makes sense if |
e84c73a8 SL |
1101 | verify is set. Defaults to 1. |
1102 | ||
71bfa161 JA |
1103 | verify=str If writing to a file, fio can verify the file contents |
1104 | after each iteration of the job. The allowed values are: | |
1105 | ||
1106 | md5 Use an md5 sum of the data area and store | |
1107 | it in the header of each block. | |
1108 | ||
17dc34df JA |
1109 | crc64 Use an experimental crc64 sum of the data |
1110 | area and store it in the header of each | |
1111 | block. | |
1112 | ||
bac39e0e JA |
1113 | crc32c Use a crc32c sum of the data area and store |
1114 | it in the header of each block. | |
1115 | ||
3845591f | 1116 | crc32c-intel Use hardware assisted crc32c calcuation |
0539d758 JA |
1117 | provided on SSE4.2 enabled processors. Falls |
1118 | back to regular software crc32c, if not | |
1119 | supported by the system. | |
3845591f | 1120 | |
71bfa161 JA |
1121 | crc32 Use a crc32 sum of the data area and store |
1122 | it in the header of each block. | |
1123 | ||
969f7ed3 JA |
1124 | crc16 Use a crc16 sum of the data area and store |
1125 | it in the header of each block. | |
1126 | ||
17dc34df JA |
1127 | crc7 Use a crc7 sum of the data area and store |
1128 | it in the header of each block. | |
1129 | ||
844ea602 JA |
1130 | xxhash Use xxhash as the checksum function. Generally |
1131 | the fastest software checksum that fio | |
1132 | supports. | |
1133 | ||
cd14cc10 JA |
1134 | sha512 Use sha512 as the checksum function. |
1135 | ||
1136 | sha256 Use sha256 as the checksum function. | |
1137 | ||
7c353ceb JA |
1138 | sha1 Use optimized sha1 as the checksum function. |
1139 | ||
7437ee87 SL |
1140 | meta Write extra information about each io |
1141 | (timestamp, block number etc.). The block | |
62167762 JC |
1142 | number is verified. The io sequence number is |
1143 | verified for workloads that write data. | |
1144 | See also verify_pattern. | |
7437ee87 | 1145 | |
36690c9b JA |
1146 | null Only pretend to verify. Useful for testing |
1147 | internals with ioengine=null, not for much | |
1148 | else. | |
1149 | ||
6c219763 | 1150 | This option can be used for repeated burn-in tests of a |
71bfa161 | 1151 | system to make sure that the written data is also |
b892dc08 JA |
1152 | correctly read back. If the data direction given is |
1153 | a read or random read, fio will assume that it should | |
1154 | verify a previously written file. If the data direction | |
1155 | includes any form of write, the verify will be of the | |
1156 | newly written data. | |
71bfa161 | 1157 | |
160b966d JA |
1158 | verifysort=bool If set, fio will sort written verify blocks when it deems |
1159 | it faster to read them back in a sorted manner. This is | |
1160 | often the case when overwriting an existing file, since | |
1161 | the blocks are already laid out in the file system. You | |
1162 | can ignore this option unless doing huge amounts of really | |
1163 | fast IO where the red-black tree sorting CPU time becomes | |
1164 | significant. | |
3f9f4e26 | 1165 | |
f7fa2653 | 1166 | verify_offset=int Swap the verification header with data somewhere else |
546a9142 SL |
1167 | in the block before writing. Its swapped back before |
1168 | verifying. | |
1169 | ||
f7fa2653 | 1170 | verify_interval=int Write the verification header at a finer granularity |
3f9f4e26 SL |
1171 | than the blocksize. It will be written for chunks the |
1172 | size of header_interval. blocksize should divide this | |
1173 | evenly. | |
90059d65 | 1174 | |
0e92f873 | 1175 | verify_pattern=str If set, fio will fill the io buffers with this |
e28218f3 SL |
1176 | pattern. Fio defaults to filling with totally random |
1177 | bytes, but sometimes it's interesting to fill with a known | |
1178 | pattern for io verification purposes. Depending on the | |
1179 | width of the pattern, fio will fill 1/2/3/4 bytes of the | |
0e92f873 RR |
1180 | buffer at the time(it can be either a decimal or a hex number). |
1181 | The verify_pattern if larger than a 32-bit quantity has to | |
996093bb JA |
1182 | be a hex number that starts with either "0x" or "0X". Use |
1183 | with verify=meta. | |
e28218f3 | 1184 | |
68e1f29a | 1185 | verify_fatal=bool Normally fio will keep checking the entire contents |
a12a3b4d JA |
1186 | before quitting on a block verification failure. If this |
1187 | option is set, fio will exit the job on the first observed | |
1188 | failure. | |
e8462bd8 | 1189 | |
b463e936 JA |
1190 | verify_dump=bool If set, dump the contents of both the original data |
1191 | block and the data block we read off disk to files. This | |
1192 | allows later analysis to inspect just what kind of data | |
ef71e317 | 1193 | corruption occurred. Off by default. |
b463e936 | 1194 | |
e8462bd8 JA |
1195 | verify_async=int Fio will normally verify IO inline from the submitting |
1196 | thread. This option takes an integer describing how many | |
1197 | async offload threads to create for IO verification instead, | |
1198 | causing fio to offload the duty of verifying IO contents | |
c85c324c JA |
1199 | to one or more separate threads. If using this offload |
1200 | option, even sync IO engines can benefit from using an | |
1201 | iodepth setting higher than 1, as it allows them to have | |
1202 | IO in flight while verifies are running. | |
e8462bd8 JA |
1203 | |
1204 | verify_async_cpus=str Tell fio to set the given CPU affinity on the | |
1205 | async IO verification threads. See cpus_allowed for the | |
1206 | format used. | |
6f87418f JA |
1207 | |
1208 | verify_backlog=int Fio will normally verify the written contents of a | |
1209 | job that utilizes verify once that job has completed. In | |
1210 | other words, everything is written then everything is read | |
1211 | back and verified. You may want to verify continually | |
1212 | instead for a variety of reasons. Fio stores the meta data | |
1213 | associated with an IO block in memory, so for large | |
1214 | verify workloads, quite a bit of memory would be used up | |
1215 | holding this meta data. If this option is enabled, fio | |
f42195a3 JA |
1216 | will write only N blocks before verifying these blocks. |
1217 | ||
6f87418f JA |
1218 | verify_backlog_batch=int Control how many blocks fio will verify |
1219 | if verify_backlog is set. If not set, will default to | |
1220 | the value of verify_backlog (meaning the entire queue | |
f42195a3 JA |
1221 | is read back and verified). If verify_backlog_batch is |
1222 | less than verify_backlog then not all blocks will be verified, | |
1223 | if verify_backlog_batch is larger than verify_backlog, some | |
1224 | blocks will be verified more than once. | |
66c098b8 | 1225 | |
d392365e | 1226 | stonewall |
de8f6de9 | 1227 | wait_for_previous Wait for preceding jobs in the job file to exit, before |
71bfa161 | 1228 | starting this one. Can be used to insert serialization |
b3d62a75 JA |
1229 | points in the job file. A stone wall also implies starting |
1230 | a new reporting group. | |
1231 | ||
abcab6af | 1232 | new_group Start a new reporting group. See: group_reporting. |
71bfa161 JA |
1233 | |
1234 | numjobs=int Create the specified number of clones of this job. May be | |
1235 | used to setup a larger number of threads/processes doing | |
abcab6af AV |
1236 | the same thing. Each thread is reported separately; to see |
1237 | statistics for all clones as a whole, use group_reporting in | |
1238 | conjunction with new_group. | |
1239 | ||
1240 | group_reporting It may sometimes be interesting to display statistics for | |
04b2f799 JA |
1241 | groups of jobs as a whole instead of for each individual job. |
1242 | This is especially true if 'numjobs' is used; looking at | |
1243 | individual thread/process output quickly becomes unwieldy. | |
1244 | To see the final report per-group instead of per-job, use | |
1245 | 'group_reporting'. Jobs in a file will be part of the same | |
1246 | reporting group, unless if separated by a stonewall, or by | |
1247 | using 'new_group'. | |
71bfa161 JA |
1248 | |
1249 | thread fio defaults to forking jobs, however if this option is | |
1250 | given, fio will use pthread_create(3) to create threads | |
1251 | instead. | |
1252 | ||
f7fa2653 | 1253 | zonesize=int Divide a file into zones of the specified size. See zoneskip. |
71bfa161 | 1254 | |
f7fa2653 | 1255 | zoneskip=int Skip the specified number of bytes when zonesize data has |
71bfa161 JA |
1256 | been read. The two zone options can be used to only do |
1257 | io on zones of a file. | |
1258 | ||
076efc7c | 1259 | write_iolog=str Write the issued io patterns to the specified file. See |
5b42a488 SH |
1260 | read_iolog. Specify a separate file for each job, otherwise |
1261 | the iologs will be interspersed and the file may be corrupt. | |
71bfa161 | 1262 | |
076efc7c | 1263 | read_iolog=str Open an iolog with the specified file name and replay the |
71bfa161 | 1264 | io patterns it contains. This can be used to store a |
6df8adaa JA |
1265 | workload and replay it sometime later. The iolog given |
1266 | may also be a blktrace binary file, which allows fio | |
1267 | to replay a workload captured by blktrace. See blktrace | |
1268 | for how to capture such logging data. For blktrace replay, | |
1269 | the file needs to be turned into a blkparse binary data | |
ea3e51c3 | 1270 | file first (blkparse <device> -o /dev/null -d file_for_fio.bin). |
66c098b8 | 1271 | |
64bbb865 | 1272 | replay_no_stall=int When replaying I/O with read_iolog the default behavior |
62776229 JA |
1273 | is to attempt to respect the time stamps within the log and |
1274 | replay them with the appropriate delay between IOPS. By | |
1275 | setting this variable fio will not respect the timestamps and | |
1276 | attempt to replay them as fast as possible while still | |
1277 | respecting ordering. The result is the same I/O pattern to a | |
1278 | given device, but different timings. | |
71bfa161 | 1279 | |
d1c46c04 DN |
1280 | replay_redirect=str While replaying I/O patterns using read_iolog the |
1281 | default behavior is to replay the IOPS onto the major/minor | |
1282 | device that each IOP was recorded from. This is sometimes | |
de8f6de9 | 1283 | undesirable because on a different machine those major/minor |
d1c46c04 DN |
1284 | numbers can map to a different device. Changing hardware on |
1285 | the same system can also result in a different major/minor | |
1286 | mapping. Replay_redirect causes all IOPS to be replayed onto | |
1287 | the single specified device regardless of the device it was | |
1288 | recorded from. i.e. replay_redirect=/dev/sdc would cause all | |
1289 | IO in the blktrace to be replayed onto /dev/sdc. This means | |
1290 | multiple devices will be replayed onto a single, if the trace | |
1291 | contains multiple devices. If you want multiple devices to be | |
1292 | replayed concurrently to multiple redirected devices you must | |
1293 | blkparse your trace into separate traces and replay them with | |
1294 | independent fio invocations. Unfortuantely this also breaks | |
1295 | the strict time ordering between multiple device accesses. | |
1296 | ||
e3cedca7 | 1297 | write_bw_log=str If given, write a bandwidth log of the jobs in this job |
71bfa161 | 1298 | file. Can be used to store data of the bandwidth of the |
e0da9bc2 JA |
1299 | jobs in their lifetime. The included fio_generate_plots |
1300 | script uses gnuplot to turn these text files into nice | |
ddb754db LAG |
1301 | graphs. See write_lat_log for behaviour of given |
1302 | filename. For this option, the suffix is _bw.log. | |
71bfa161 | 1303 | |
e3cedca7 | 1304 | write_lat_log=str Same as write_bw_log, except that this option stores io |
02af0988 JA |
1305 | submission, completion, and total latencies instead. If no |
1306 | filename is given with this option, the default filename of | |
1307 | "jobname_type.log" is used. Even if the filename is given, | |
1308 | fio will still append the type of log. So if one specifies | |
e3cedca7 JA |
1309 | |
1310 | write_lat_log=foo | |
1311 | ||
d5d94597 | 1312 | The actual log names will be foo_slat.log, foo_clat.log, |
02af0988 JA |
1313 | and foo_lat.log. This helps fio_generate_plot fine the logs |
1314 | automatically. | |
71bfa161 | 1315 | |
b8bc8cba JA |
1316 | write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is |
1317 | given with this option, the default filename of | |
1318 | "jobname_type.log" is used. Even if the filename is given, | |
1319 | fio will still append the type of log. | |
1320 | ||
1321 | log_avg_msec=int By default, fio will log an entry in the iops, latency, | |
1322 | or bw log for every IO that completes. When writing to the | |
1323 | disk log, that can quickly grow to a very large size. Setting | |
1324 | this option makes fio average the each log entry over the | |
1325 | specified period of time, reducing the resolution of the log. | |
1326 | Defaults to 0. | |
1327 | ||
f7fa2653 | 1328 | lockmem=int Pin down the specified amount of memory with mlock(2). Can |
71bfa161 JA |
1329 | potentially be used instead of removing memory or booting |
1330 | with less memory to simulate a smaller amount of memory. | |
81c6b6cd | 1331 | The amount specified is per worker. |
71bfa161 JA |
1332 | |
1333 | exec_prerun=str Before running this job, issue the command specified | |
74c8c488 JA |
1334 | through system(3). Output is redirected in a file called |
1335 | jobname.prerun.txt. | |
71bfa161 JA |
1336 | |
1337 | exec_postrun=str After the job completes, issue the command specified | |
74c8c488 JA |
1338 | though system(3). Output is redirected in a file called |
1339 | jobname.postrun.txt. | |
71bfa161 JA |
1340 | |
1341 | ioscheduler=str Attempt to switch the device hosting the file to the specified | |
1342 | io scheduler before running. | |
1343 | ||
0a839f30 JA |
1344 | disk_util=bool Generate disk utilization statistics, if the platform |
1345 | supports it. Defaults to on. | |
1346 | ||
02af0988 | 1347 | disable_lat=bool Disable measurements of total latency numbers. Useful |
9520ebb9 JA |
1348 | only for cutting back the number of calls to gettimeofday, |
1349 | as that does impact performance at really high IOPS rates. | |
1350 | Note that to really get rid of a large amount of these | |
1351 | calls, this option must be used with disable_slat and | |
1352 | disable_bw as well. | |
1353 | ||
02af0988 JA |
1354 | disable_clat=bool Disable measurements of completion latency numbers. See |
1355 | disable_lat. | |
1356 | ||
9520ebb9 | 1357 | disable_slat=bool Disable measurements of submission latency numbers. See |
02af0988 | 1358 | disable_slat. |
9520ebb9 JA |
1359 | |
1360 | disable_bw=bool Disable measurements of throughput/bandwidth numbers. See | |
02af0988 | 1361 | disable_lat. |
9520ebb9 | 1362 | |
83349190 YH |
1363 | clat_percentiles=bool Enable the reporting of percentiles of |
1364 | completion latencies. | |
1365 | ||
1366 | percentile_list=float_list Overwrite the default list of percentiles | |
1367 | for completion latencies. Each number is a floating | |
1368 | number in the range (0,100], and the maximum length of | |
1369 | the list is 20. Use ':' to separate the numbers, and | |
1370 | list the numbers in ascending order. For example, | |
1371 | --percentile_list=99.5:99.9 will cause fio to report | |
1372 | the values of completion latency below which 99.5% and | |
1373 | 99.9% of the observed latencies fell, respectively. | |
1374 | ||
23893646 JA |
1375 | clocksource=str Use the given clocksource as the base of timing. The |
1376 | supported options are: | |
1377 | ||
1378 | gettimeofday gettimeofday(2) | |
1379 | ||
1380 | clock_gettime clock_gettime(2) | |
1381 | ||
1382 | cpu Internal CPU clock source | |
1383 | ||
1384 | cpu is the preferred clocksource if it is reliable, as it | |
1385 | is very fast (and fio is heavy on time calls). Fio will | |
1386 | automatically use this clocksource if it's supported and | |
1387 | considered reliable on the system it is running on, unless | |
1388 | another clocksource is specifically set. For x86/x86-64 CPUs, | |
1389 | this means supporting TSC Invariant. | |
1390 | ||
993bf48b JA |
1391 | gtod_reduce=bool Enable all of the gettimeofday() reducing options |
1392 | (disable_clat, disable_slat, disable_bw) plus reduce | |
1393 | precision of the timeout somewhat to really shrink | |
1394 | the gettimeofday() call count. With this option enabled, | |
1395 | we only do about 0.4% of the gtod() calls we would have | |
1396 | done if all time keeping was enabled. | |
1397 | ||
be4ecfdf JA |
1398 | gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of |
1399 | execution to just getting the current time. Fio (and | |
1400 | databases, for instance) are very intensive on gettimeofday() | |
1401 | calls. With this option, you can set one CPU aside for | |
1402 | doing nothing but logging current time to a shared memory | |
1403 | location. Then the other threads/processes that run IO | |
1404 | workloads need only copy that segment, instead of entering | |
1405 | the kernel with a gettimeofday() call. The CPU set aside | |
1406 | for doing these time calls will be excluded from other | |
1407 | uses. Fio will manually clear it from the CPU mask of other | |
1408 | jobs. | |
a696fa2a | 1409 | |
06842027 | 1410 | continue_on_error=str Normally fio will exit the job on the first observed |
f2bba182 RR |
1411 | failure. If this option is set, fio will continue the job when |
1412 | there is a 'non-fatal error' (EIO or EILSEQ) until the runtime | |
1413 | is exceeded or the I/O size specified is completed. If this | |
1414 | option is used, there are two more stats that are appended, | |
1415 | the total error count and the first error. The error field | |
1416 | given in the stats is the first error that was hit during the | |
1417 | run. | |
be4ecfdf | 1418 | |
06842027 SL |
1419 | The allowed values are: |
1420 | ||
1421 | none Exit on any IO or verify errors. | |
1422 | ||
1423 | read Continue on read errors, exit on all others. | |
1424 | ||
1425 | write Continue on write errors, exit on all others. | |
1426 | ||
1427 | io Continue on any IO error, exit on all others. | |
1428 | ||
1429 | verify Continue on verify errors, exit on all others. | |
1430 | ||
1431 | all Continue on all errors. | |
1432 | ||
1433 | 0 Backward-compatible alias for 'none'. | |
1434 | ||
1435 | 1 Backward-compatible alias for 'all'. | |
1436 | ||
8b28bd41 DM |
1437 | ignore_error=str Sometimes you want to ignore some errors during test |
1438 | in that case you can specify error list for each error type. | |
1439 | ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST | |
1440 | errors for given error type is separated with ':'. Error | |
1441 | may be symbol ('ENOSPC', 'ENOMEM') or integer. | |
1442 | Example: | |
1443 | ignore_error=EAGAIN,ENOSPC:122 | |
66c098b8 BC |
1444 | This option will ignore EAGAIN from READ, and ENOSPC and |
1445 | 122(EDQUOT) from WRITE. | |
8b28bd41 DM |
1446 | |
1447 | error_dump=bool If set dump every error even if it is non fatal, true | |
1448 | by default. If disabled only fatal error will be dumped | |
66c098b8 | 1449 | |
6adb38a1 JA |
1450 | cgroup=str Add job to this control group. If it doesn't exist, it will |
1451 | be created. The system must have a mounted cgroup blkio | |
1452 | mount point for this to work. If your system doesn't have it | |
1453 | mounted, you can do so with: | |
a696fa2a JA |
1454 | |
1455 | # mount -t cgroup -o blkio none /cgroup | |
1456 | ||
a696fa2a JA |
1457 | cgroup_weight=int Set the weight of the cgroup to this value. See |
1458 | the documentation that comes with the kernel, allowed values | |
1459 | are in the range of 100..1000. | |
71bfa161 | 1460 | |
7de87099 VG |
1461 | cgroup_nodelete=bool Normally fio will delete the cgroups it has created after |
1462 | the job completion. To override this behavior and to leave | |
1463 | cgroups around after the job completion, set cgroup_nodelete=1. | |
1464 | This can be useful if one wants to inspect various cgroup | |
1465 | files after job completion. Default: false | |
1466 | ||
e0b0d892 JA |
1467 | uid=int Instead of running as the invoking user, set the user ID to |
1468 | this value before the thread/process does any work. | |
1469 | ||
1470 | gid=int Set group ID, see uid. | |
1471 | ||
9e684a49 DE |
1472 | flow_id=int The ID of the flow. If not specified, it defaults to being a |
1473 | global flow. See flow. | |
1474 | ||
1475 | flow=int Weight in token-based flow control. If this value is used, then | |
1476 | there is a 'flow counter' which is used to regulate the | |
1477 | proportion of activity between two or more jobs. fio attempts | |
1478 | to keep this flow counter near zero. The 'flow' parameter | |
1479 | stands for how much should be added or subtracted to the flow | |
1480 | counter on each iteration of the main I/O loop. That is, if | |
1481 | one job has flow=8 and another job has flow=-1, then there | |
1482 | will be a roughly 1:8 ratio in how much one runs vs the other. | |
1483 | ||
1484 | flow_watermark=int The maximum value that the absolute value of the flow | |
1485 | counter is allowed to reach before the job must wait for a | |
1486 | lower value of the counter. | |
1487 | ||
1488 | flow_sleep=int The period of time, in microseconds, to wait after the flow | |
1489 | watermark has been exceeded before retrying operations | |
1490 | ||
de890a1e SL |
1491 | In addition, there are some parameters which are only valid when a specific |
1492 | ioengine is in use. These are used identically to normal parameters, with the | |
1493 | caveat that when used on the command line, they must come after the ioengine | |
1494 | that defines them is selected. | |
1495 | ||
1496 | [libaio] userspace_reap Normally, with the libaio engine in use, fio will use | |
1497 | the io_getevents system call to reap newly returned events. | |
1498 | With this flag turned on, the AIO ring will be read directly | |
1499 | from user-space to reap events. The reaping mode is only | |
1500 | enabled when polling for a minimum of 0 events (eg when | |
1501 | iodepth_batch_complete=0). | |
1502 | ||
0353050f JA |
1503 | [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles. |
1504 | ||
1505 | [cpu] cpuchunks=int Split the load into cycles of the given time. In | |
1506 | microseconds. | |
1507 | ||
de890a1e SL |
1508 | [netsplice] hostname=str |
1509 | [net] hostname=str The host name or IP address to use for TCP or UDP based IO. | |
1510 | If the job is a TCP listener or UDP reader, the hostname is not | |
b511c9aa SB |
1511 | used and must be omitted unless it is a valid UDP multicast |
1512 | address. | |
de890a1e SL |
1513 | |
1514 | [netsplice] port=int | |
1515 | [net] port=int The TCP or UDP port to bind to or connect to. | |
1516 | ||
b93b6a2e SB |
1517 | [netsplice] interface=str |
1518 | [net] interface=str The IP address of the network interface used to send or | |
1519 | receive UDP multicast | |
1520 | ||
d3a623de SB |
1521 | [netsplice] ttl=int |
1522 | [net] ttl=int Time-to-live value for outgoing UDP multicast packets. | |
1523 | Default: 1 | |
1524 | ||
1d360ffb JA |
1525 | [netsplice] nodelay=bool |
1526 | [net] nodelay=bool Set TCP_NODELAY on TCP connections. | |
1527 | ||
de890a1e SL |
1528 | [netsplice] protocol=str |
1529 | [netsplice] proto=str | |
1530 | [net] protocol=str | |
1531 | [net] proto=str The network protocol to use. Accepted values are: | |
1532 | ||
1533 | tcp Transmission control protocol | |
49ccb8c1 | 1534 | tcpv6 Transmission control protocol V6 |
f5cc3d0e | 1535 | udp User datagram protocol |
49ccb8c1 | 1536 | udpv6 User datagram protocol V6 |
de890a1e SL |
1537 | unix UNIX domain socket |
1538 | ||
1539 | When the protocol is TCP or UDP, the port must also be given, | |
1540 | as well as the hostname if the job is a TCP listener or UDP | |
1541 | reader. For unix sockets, the normal filename option should be | |
1542 | used and the port is invalid. | |
1543 | ||
1544 | [net] listen For TCP network connections, tell fio to listen for incoming | |
1545 | connections rather than initiating an outgoing connection. The | |
1546 | hostname must be omitted if this option is used. | |
b511c9aa | 1547 | [net] pingpong Normaly a network writer will just continue writing data, and |
7aeb1e94 JA |
1548 | a network reader will just consume packages. If pingpong=1 |
1549 | is set, a writer will send its normal payload to the reader, | |
1550 | then wait for the reader to send the same payload back. This | |
1551 | allows fio to measure network latencies. The submission | |
1552 | and completion latencies then measure local time spent | |
1553 | sending or receiving, and the completion latency measures | |
1554 | how long it took for the other end to receive and send back. | |
b511c9aa SB |
1555 | For UDP multicast traffic pingpong=1 should only be set for a |
1556 | single reader when multiple readers are listening to the same | |
1557 | address. | |
7aeb1e94 | 1558 | |
d54fce84 DM |
1559 | [e4defrag] donorname=str |
1560 | File will be used as a block donor(swap extents between files) | |
1561 | [e4defrag] inplace=int | |
66c098b8 | 1562 | Configure donor file blocks allocation strategy |
d54fce84 DM |
1563 | 0(default): Preallocate donor's file on init |
1564 | 1 : allocate space immidietly inside defragment event, | |
1565 | and free right after event | |
1566 | ||
de890a1e SL |
1567 | |
1568 | ||
71bfa161 JA |
1569 | 6.0 Interpreting the output |
1570 | --------------------------- | |
1571 | ||
1572 | fio spits out a lot of output. While running, fio will display the | |
1573 | status of the jobs created. An example of that would be: | |
1574 | ||
73c8b082 | 1575 | Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] |
71bfa161 JA |
1576 | |
1577 | The characters inside the square brackets denote the current status of | |
1578 | each thread. The possible values (in typical life cycle order) are: | |
1579 | ||
1580 | Idle Run | |
1581 | ---- --- | |
1582 | P Thread setup, but not started. | |
1583 | C Thread created. | |
9c6f6316 | 1584 | I Thread initialized, waiting or generating necessary data. |
b0f65863 | 1585 | p Thread running pre-reading file(s). |
71bfa161 JA |
1586 | R Running, doing sequential reads. |
1587 | r Running, doing random reads. | |
1588 | W Running, doing sequential writes. | |
1589 | w Running, doing random writes. | |
1590 | M Running, doing mixed sequential reads/writes. | |
1591 | m Running, doing mixed random reads/writes. | |
1592 | F Running, currently waiting for fsync() | |
fc6bd43c | 1593 | V Running, doing verification of written data. |
71bfa161 | 1594 | E Thread exited, not reaped by main thread yet. |
4f7e57a4 JA |
1595 | _ Thread reaped, or |
1596 | X Thread reaped, exited with an error. | |
a5e371a6 | 1597 | K Thread reaped, exited due to signal. |
71bfa161 JA |
1598 | |
1599 | The other values are fairly self explanatory - number of threads | |
c9f60304 JA |
1600 | currently running and doing io, rate of io since last check (read speed |
1601 | listed first, then write speed), and the estimated completion percentage | |
1602 | and time for the running group. It's impossible to estimate runtime of | |
4f7e57a4 JA |
1603 | the following groups (if any). Note that the string is displayed in order, |
1604 | so it's possible to tell which of the jobs are currently doing what. The | |
1605 | first character is the first job defined in the job file, and so forth. | |
71bfa161 JA |
1606 | |
1607 | When fio is done (or interrupted by ctrl-c), it will show the data for | |
1608 | each thread, group of threads, and disks in that order. For each data | |
1609 | direction, the output looks like: | |
1610 | ||
1611 | Client1 (g=0): err= 0: | |
35649e58 | 1612 | write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec |
6104ddb6 JA |
1613 | slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92 |
1614 | clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82 | |
b22989b9 | 1615 | bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68 |
e7823a94 | 1616 | cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17 |
71619dc2 | 1617 | IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% |
838bc709 JA |
1618 | submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% |
1619 | complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% | |
30061b97 | 1620 | issued r/w: total=0/32768, short=0/0 |
8abdce66 JA |
1621 | lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%, |
1622 | lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0% | |
71bfa161 JA |
1623 | |
1624 | The client number is printed, along with the group id and error of that | |
1625 | thread. Below is the io statistics, here for writes. In the order listed, | |
1626 | they denote: | |
1627 | ||
1628 | io= Number of megabytes io performed | |
1629 | bw= Average bandwidth rate | |
35649e58 | 1630 | iops= Average IOs performed per second |
71bfa161 | 1631 | runt= The runtime of that thread |
72fbda2a | 1632 | slat= Submission latency (avg being the average, stdev being the |
71bfa161 JA |
1633 | standard deviation). This is the time it took to submit |
1634 | the io. For sync io, the slat is really the completion | |
8a35c71e | 1635 | latency, since queue/complete is one operation there. This |
bf9a3edb | 1636 | value can be in milliseconds or microseconds, fio will choose |
8a35c71e | 1637 | the most appropriate base and print that. In the example |
0d237712 LAG |
1638 | above, milliseconds is the best scale. Note: in --minimal mode |
1639 | latencies are always expressed in microseconds. | |
71bfa161 JA |
1640 | clat= Completion latency. Same names as slat, this denotes the |
1641 | time from submission to completion of the io pieces. For | |
1642 | sync io, clat will usually be equal (or very close) to 0, | |
1643 | as the time from submit to complete is basically just | |
1644 | CPU time (io has already been done, see slat explanation). | |
1645 | bw= Bandwidth. Same names as the xlat stats, but also includes | |
1646 | an approximate percentage of total aggregate bandwidth | |
1647 | this thread received in this group. This last value is | |
1648 | only really useful if the threads in this group are on the | |
1649 | same disk, since they are then competing for disk access. | |
1650 | cpu= CPU usage. User and system time, along with the number | |
e7823a94 JA |
1651 | of context switches this thread went through, usage of |
1652 | system and user time, and finally the number of major | |
1653 | and minor page faults. | |
71619dc2 JA |
1654 | IO depths= The distribution of io depths over the job life time. The |
1655 | numbers are divided into powers of 2, so for example the | |
1656 | 16= entries includes depths up to that value but higher | |
1657 | than the previous entry. In other words, it covers the | |
1658 | range from 16 to 31. | |
838bc709 JA |
1659 | IO submit= How many pieces of IO were submitting in a single submit |
1660 | call. Each entry denotes that amount and below, until | |
1661 | the previous entry - eg, 8=100% mean that we submitted | |
1662 | anywhere in between 5-8 ios per submit call. | |
1663 | IO complete= Like the above submit number, but for completions instead. | |
30061b97 JA |
1664 | IO issued= The number of read/write requests issued, and how many |
1665 | of them were short. | |
ec118304 JA |
1666 | IO latencies= The distribution of IO completion latencies. This is the |
1667 | time from when IO leaves fio and when it gets completed. | |
1668 | The numbers follow the same pattern as the IO depths, | |
1669 | meaning that 2=1.6% means that 1.6% of the IO completed | |
8abdce66 JA |
1670 | within 2 msecs, 20=12.8% means that 12.8% of the IO |
1671 | took more than 10 msecs, but less than (or equal to) 20 msecs. | |
71bfa161 JA |
1672 | |
1673 | After each client has been listed, the group statistics are printed. They | |
1674 | will look like this: | |
1675 | ||
1676 | Run status group 0 (all jobs): | |
b22989b9 JA |
1677 | READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec |
1678 | WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec | |
71bfa161 JA |
1679 | |
1680 | For each data direction, it prints: | |
1681 | ||
1682 | io= Number of megabytes io performed. | |
1683 | aggrb= Aggregate bandwidth of threads in this group. | |
1684 | minb= The minimum average bandwidth a thread saw. | |
1685 | maxb= The maximum average bandwidth a thread saw. | |
1686 | mint= The smallest runtime of the threads in that group. | |
1687 | maxt= The longest runtime of the threads in that group. | |
1688 | ||
1689 | And finally, the disk statistics are printed. They will look like this: | |
1690 | ||
1691 | Disk stats (read/write): | |
1692 | sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00% | |
1693 | ||
1694 | Each value is printed for both reads and writes, with reads first. The | |
1695 | numbers denote: | |
1696 | ||
1697 | ios= Number of ios performed by all groups. | |
1698 | merge= Number of merges io the io scheduler. | |
1699 | ticks= Number of ticks we kept the disk busy. | |
1700 | io_queue= Total time spent in the disk queue. | |
1701 | util= The disk utilization. A value of 100% means we kept the disk | |
1702 | busy constantly, 50% would be a disk idling half of the time. | |
1703 | ||
8423bd11 JA |
1704 | It is also possible to get fio to dump the current output while it is |
1705 | running, without terminating the job. To do that, send fio the USR1 signal. | |
06464907 JA |
1706 | You can also get regularly timed dumps by using the --status-interval |
1707 | parameter, or by creating a file in /tmp named fio-dump-status. If fio | |
1708 | sees this file, it will unlink it and dump the current output status. | |
8423bd11 | 1709 | |
71bfa161 JA |
1710 | |
1711 | 7.0 Terse output | |
1712 | ---------------- | |
1713 | ||
1714 | For scripted usage where you typically want to generate tables or graphs | |
6af019c9 | 1715 | of the results, fio can output the results in a semicolon separated format. |
71bfa161 JA |
1716 | The format is one long line of values, such as: |
1717 | ||
562c2d2f DN |
1718 | 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00% |
1719 | A description of this job goes here. | |
1720 | ||
1721 | The job description (if provided) follows on a second line. | |
71bfa161 | 1722 | |
525c2bfa JA |
1723 | To enable terse output, use the --minimal command line option. The first |
1724 | value is the version of the terse output format. If the output has to | |
1725 | be changed for some reason, this number will be incremented by 1 to | |
1726 | signify that change. | |
6820cb3b | 1727 | |
71bfa161 JA |
1728 | Split up, the format is as follows: |
1729 | ||
5e726d0a | 1730 | terse version, fio version, jobname, groupid, error |
71bfa161 | 1731 | READ status: |
312b4af2 | 1732 | Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec) |
de196b82 JA |
1733 | Submission latency: min, max, mean, deviation (usec) |
1734 | Completion latency: min, max, mean, deviation (usec) | |
1db92cb6 | 1735 | Completion latency percentiles: 20 fields (see below) |
de196b82 | 1736 | Total latency: min, max, mean, deviation (usec) |
0d237712 | 1737 | Bw (KB/s): min, max, aggregate percentage of total, mean, deviation |
71bfa161 | 1738 | WRITE status: |
312b4af2 | 1739 | Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec) |
de196b82 JA |
1740 | Submission latency: min, max, mean, deviation (usec) |
1741 | Completion latency: min, max, mean, deviation (usec) | |
1db92cb6 | 1742 | Completion latency percentiles: 20 fields (see below) |
de196b82 | 1743 | Total latency: min, max, mean, deviation (usec) |
0d237712 | 1744 | Bw (KB/s): min, max, aggregate percentage of total, mean, deviation |
046ee302 | 1745 | CPU usage: user, system, context switches, major faults, minor faults |
2270890c | 1746 | IO depths: <=1, 2, 4, 8, 16, 32, >=64 |
562c2d2f DN |
1747 | IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000 |
1748 | IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000 | |
f2f788dd JA |
1749 | Disk utilization: Disk name, Read ios, write ios, |
1750 | Read merges, write merges, | |
1751 | Read ticks, write ticks, | |
3d7cd9b4 | 1752 | Time spent in queue, disk utilization percentage |
de8f6de9 | 1753 | Additional Info (dependent on continue_on_error, default off): total # errors, first error code |
66c098b8 | 1754 | |
de8f6de9 | 1755 | Additional Info (dependent on description being set): Text description |
25c8b9d7 | 1756 | |
1db92cb6 JA |
1757 | Completion latency percentiles can be a grouping of up to 20 sets, so |
1758 | for the terse output fio writes all of them. Each field will look like this: | |
1759 | ||
1760 | 1.00%=6112 | |
1761 | ||
1762 | which is the Xth percentile, and the usec latency associated with it. | |
1763 | ||
f2f788dd JA |
1764 | For disk utilization, all disks used by fio are shown. So for each disk |
1765 | there will be a disk utilization section. | |
1766 | ||
25c8b9d7 PD |
1767 | |
1768 | 8.0 Trace file format | |
1769 | --------------------- | |
66c098b8 | 1770 | There are two trace file format that you can encounter. The older (v1) format |
25c8b9d7 PD |
1771 | is unsupported since version 1.20-rc3 (March 2008). It will still be described |
1772 | below in case that you get an old trace and want to understand it. | |
1773 | ||
1774 | In any case the trace is a simple text file with a single action per line. | |
1775 | ||
1776 | ||
1777 | 8.1 Trace file format v1 | |
1778 | ------------------------ | |
1779 | Each line represents a single io action in the following format: | |
1780 | ||
1781 | rw, offset, length | |
1782 | ||
1783 | where rw=0/1 for read/write, and the offset and length entries being in bytes. | |
1784 | ||
1785 | This format is not supported in Fio versions => 1.20-rc3. | |
1786 | ||
1787 | ||
1788 | 8.2 Trace file format v2 | |
1789 | ------------------------ | |
1790 | The second version of the trace file format was added in Fio version 1.17. | |
1791 | It allows to access more then one file per trace and has a bigger set of | |
1792 | possible file actions. | |
1793 | ||
1794 | The first line of the trace file has to be: | |
1795 | ||
1796 | fio version 2 iolog | |
1797 | ||
1798 | Following this can be lines in two different formats, which are described below. | |
1799 | ||
1800 | The file management format: | |
1801 | ||
1802 | filename action | |
1803 | ||
1804 | The filename is given as an absolute path. The action can be one of these: | |
1805 | ||
1806 | add Add the given filename to the trace | |
66c098b8 | 1807 | open Open the file with the given filename. The filename has to have |
25c8b9d7 PD |
1808 | been added with the add action before. |
1809 | close Close the file with the given filename. The file has to have been | |
1810 | opened before. | |
1811 | ||
1812 | ||
1813 | The file io action format: | |
1814 | ||
1815 | filename action offset length | |
1816 | ||
1817 | The filename is given as an absolute path, and has to have been added and opened | |
66c098b8 | 1818 | before it can be used with this format. The offset and length are given in |
25c8b9d7 PD |
1819 | bytes. The action can be one of these: |
1820 | ||
1821 | wait Wait for 'offset' microseconds. Everything below 100 is discarded. | |
1822 | read Read 'length' bytes beginning from 'offset' | |
1823 | write Write 'length' bytes beginning from 'offset' | |
1824 | sync fsync() the file | |
1825 | datasync fdatasync() the file | |
1826 | trim trim the given file from the given 'offset' for 'length' bytes | |
f2a2ce0e HL |
1827 | |
1828 | ||
1829 | 9.0 CPU idleness profiling | |
06464907 | 1830 | -------------------------- |
f2a2ce0e HL |
1831 | In some cases, we want to understand CPU overhead in a test. For example, |
1832 | we test patches for the specific goodness of whether they reduce CPU usage. | |
1833 | fio implements a balloon approach to create a thread per CPU that runs at | |
1834 | idle priority, meaning that it only runs when nobody else needs the cpu. | |
1835 | By measuring the amount of work completed by the thread, idleness of each | |
1836 | CPU can be derived accordingly. | |
1837 | ||
1838 | An unit work is defined as touching a full page of unsigned characters. Mean | |
1839 | and standard deviation of time to complete an unit work is reported in "unit | |
1840 | work" section. Options can be chosen to report detailed percpu idleness or | |
1841 | overall system idleness by aggregating percpu stats. |