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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 | |
11 | ||
12 | ||
13 | 1.0 Overview and history | |
14 | ------------------------ | |
15 | fio was originally written to save me the hassle of writing special test | |
16 | case programs when I wanted to test a specific workload, either for | |
17 | performance reasons or to find/reproduce a bug. The process of writing | |
18 | such a test app can be tiresome, especially if you have to do it often. | |
19 | Hence I needed a tool that would be able to simulate a given io workload | |
20 | without resorting to writing a tailored test case again and again. | |
21 | ||
22 | A test work load is difficult to define, though. There can be any number | |
23 | of processes or threads involved, and they can each be using their own | |
24 | way of generating io. You could have someone dirtying large amounts of | |
25 | memory in an memory mapped file, or maybe several threads issuing | |
26 | reads using asynchronous io. fio needed to be flexible enough to | |
27 | simulate both of these cases, and many more. | |
28 | ||
29 | 2.0 How fio works | |
30 | ----------------- | |
31 | The first step in getting fio to simulate a desired io workload, is | |
32 | writing a job file describing that specific setup. A job file may contain | |
33 | any number of threads and/or files - the typical contents of the job file | |
34 | is a global section defining shared parameters, and one or more job | |
35 | sections describing the jobs involved. When run, fio parses this file | |
36 | and sets everything up as described. If we break down a job from top to | |
37 | bottom, it contains the following basic parameters: | |
38 | ||
39 | IO type Defines the io pattern issued to the file(s). | |
40 | We may only be reading sequentially from this | |
41 | file(s), or we may be writing randomly. Or even | |
42 | mixing reads and writes, sequentially or randomly. | |
43 | ||
44 | Block size In how large chunks are we issuing io? This may be | |
45 | a single value, or it may describe a range of | |
46 | block sizes. | |
47 | ||
48 | IO size How much data are we going to be reading/writing. | |
49 | ||
50 | IO engine How do we issue io? We could be memory mapping the | |
51 | file, we could be using regular read/write, we | |
d0ff85df | 52 | could be using splice, async io, syslet, or even |
71bfa161 JA |
53 | SG (SCSI generic sg). |
54 | ||
6c219763 | 55 | IO depth If the io engine is async, how large a queuing |
71bfa161 JA |
56 | depth do we want to maintain? |
57 | ||
58 | IO type Should we be doing buffered io, or direct/raw io? | |
59 | ||
60 | Num files How many files are we spreading the workload over. | |
61 | ||
62 | Num threads How many threads or processes should we spread | |
63 | this workload over. | |
64 | ||
65 | The above are the basic parameters defined for a workload, in addition | |
66 | there's a multitude of parameters that modify other aspects of how this | |
67 | job behaves. | |
68 | ||
69 | ||
70 | 3.0 Running fio | |
71 | --------------- | |
72 | See the README file for command line parameters, there are only a few | |
73 | of them. | |
74 | ||
75 | Running fio is normally the easiest part - you just give it the job file | |
76 | (or job files) as parameters: | |
77 | ||
78 | $ fio job_file | |
79 | ||
80 | and it will start doing what the job_file tells it to do. You can give | |
81 | more than one job file on the command line, fio will serialize the running | |
82 | of those files. Internally that is the same as using the 'stonewall' | |
83 | parameter described the the parameter section. | |
84 | ||
b4692828 JA |
85 | If the job file contains only one job, you may as well just give the |
86 | parameters on the command line. The command line parameters are identical | |
87 | to the job parameters, with a few extra that control global parameters | |
88 | (see README). For example, for the job file parameter iodepth=2, the | |
c2b1e753 JA |
89 | mirror command line option would be --iodepth 2 or --iodepth=2. You can |
90 | also use the command line for giving more than one job entry. For each | |
91 | --name option that fio sees, it will start a new job with that name. | |
92 | Command line entries following a --name entry will apply to that job, | |
93 | until there are no more entries or a new --name entry is seen. This is | |
94 | similar to the job file options, where each option applies to the current | |
95 | job until a new [] job entry is seen. | |
b4692828 | 96 | |
71bfa161 JA |
97 | fio does not need to run as root, except if the files or devices specified |
98 | in the job section requires that. Some other options may also be restricted, | |
6c219763 | 99 | such as memory locking, io scheduler switching, and decreasing the nice value. |
71bfa161 JA |
100 | |
101 | ||
102 | 4.0 Job file format | |
103 | ------------------- | |
104 | As previously described, fio accepts one or more job files describing | |
105 | what it is supposed to do. The job file format is the classic ini file, | |
106 | where the names enclosed in [] brackets define the job name. You are free | |
107 | to use any ascii name you want, except 'global' which has special meaning. | |
108 | A global section sets defaults for the jobs described in that file. A job | |
109 | may override a global section parameter, and a job file may even have | |
110 | several global sections if so desired. A job is only affected by a global | |
65db0851 JA |
111 | section residing above it. If the first character in a line is a ';' or a |
112 | '#', the entire line is discarded as a comment. | |
71bfa161 JA |
113 | |
114 | So lets look at a really simple job file that define to threads, each | |
115 | randomly reading from a 128MiB file. | |
116 | ||
117 | ; -- start job file -- | |
118 | [global] | |
119 | rw=randread | |
120 | size=128m | |
121 | ||
122 | [job1] | |
123 | ||
124 | [job2] | |
125 | ||
126 | ; -- end job file -- | |
127 | ||
128 | As you can see, the job file sections themselves are empty as all the | |
129 | described parameters are shared. As no filename= option is given, fio | |
c2b1e753 JA |
130 | makes up a filename for each of the jobs as it sees fit. On the command |
131 | line, this job would look as follows: | |
132 | ||
133 | $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2 | |
134 | ||
71bfa161 JA |
135 | |
136 | Lets look at an example that have a number of processes writing randomly | |
137 | to files. | |
138 | ||
139 | ; -- start job file -- | |
140 | [random-writers] | |
141 | ioengine=libaio | |
142 | iodepth=4 | |
143 | rw=randwrite | |
144 | bs=32k | |
145 | direct=0 | |
146 | size=64m | |
147 | numjobs=4 | |
148 | ||
149 | ; -- end job file -- | |
150 | ||
151 | Here we have no global section, as we only have one job defined anyway. | |
152 | We want to use async io here, with a depth of 4 for each file. We also | |
153 | increased the buffer size used to 32KiB and define numjobs to 4 to | |
154 | fork 4 identical jobs. The result is 4 processes each randomly writing | |
b4692828 JA |
155 | to their own 64MiB file. Instead of using the above job file, you could |
156 | have given the parameters on the command line. For this case, you would | |
157 | specify: | |
158 | ||
159 | $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4 | |
71bfa161 JA |
160 | |
161 | fio ships with a few example job files, you can also look there for | |
162 | inspiration. | |
163 | ||
164 | ||
165 | 5.0 Detailed list of parameters | |
166 | ------------------------------- | |
167 | ||
168 | This section describes in details each parameter associated with a job. | |
169 | Some parameters take an option of a given type, such as an integer or | |
170 | a string. The following types are used: | |
171 | ||
172 | str String. This is a sequence of alpha characters. | |
173 | int Integer. A whole number value, may be negative. | |
174 | siint SI integer. A whole number value, which may contain a postfix | |
175 | describing the base of the number. Accepted postfixes are k/m/g, | |
6c219763 | 176 | meaning kilo, mega, and giga. So if you want to specify 4096, |
71bfa161 JA |
177 | you could either write out '4096' or just give 4k. The postfixes |
178 | signify base 2 values, so 1024 is 1k and 1024k is 1m and so on. | |
179 | bool Boolean. Usually parsed as an integer, however only defined for | |
180 | true and false (1 and 0). | |
181 | irange Integer range with postfix. Allows value range to be given, such | |
0c9baf91 JA |
182 | as 1024-4096. A colon may also be used as the seperator, eg |
183 | 1k:4k. If the option allows two sets of ranges, they can be | |
184 | specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see | |
185 | siint. | |
71bfa161 JA |
186 | |
187 | With the above in mind, here follows the complete list of fio job | |
188 | parameters. | |
189 | ||
190 | name=str ASCII name of the job. This may be used to override the | |
191 | name printed by fio for this job. Otherwise the job | |
c2b1e753 | 192 | name is used. On the command line this parameter has the |
6c219763 | 193 | special purpose of also signaling the start of a new |
c2b1e753 | 194 | job. |
71bfa161 | 195 | |
61697c37 JA |
196 | description=str Text description of the job. Doesn't do anything except |
197 | dump this text description when this job is run. It's | |
198 | not parsed. | |
199 | ||
71bfa161 JA |
200 | directory=str Prefix filenames with this directory. Used to places files |
201 | in a different location than "./". | |
202 | ||
203 | filename=str Fio normally makes up a filename based on the job name, | |
204 | thread number, and file number. If you want to share | |
205 | files between threads in a job or several jobs, specify | |
ed92ac0c JA |
206 | a filename for each of them to override the default. If |
207 | the ioengine used is 'net', the filename is the host and | |
208 | port to connect to in the format of =host:port. | |
71bfa161 JA |
209 | |
210 | rw=str Type of io pattern. Accepted values are: | |
211 | ||
212 | read Sequential reads | |
213 | write Sequential writes | |
214 | randwrite Random writes | |
215 | randread Random reads | |
216 | rw Sequential mixed reads and writes | |
217 | randrw Random mixed reads and writes | |
218 | ||
219 | For the mixed io types, the default is to split them 50/50. | |
220 | For certain types of io the result may still be skewed a bit, | |
221 | since the speed may be different. | |
222 | ||
ee738499 JA |
223 | randrepeat=bool For random IO workloads, seed the generator in a predictable |
224 | way so that results are repeatable across repetitions. | |
225 | ||
71bfa161 JA |
226 | size=siint The total size of file io for this job. This may describe |
227 | the size of the single file the job uses, or it may be | |
228 | divided between the number of files in the job. If the | |
229 | file already exists, the file size will be adjusted to this | |
230 | size if larger than the current file size. If this parameter | |
231 | is not given and the file exists, the file size will be used. | |
232 | ||
f90eff5a JA |
233 | bs=siint The block size used for the io units. Defaults to 4k. Values |
234 | can be given for both read and writes. If a single siint is | |
235 | given, it will apply to both. If a second siint is specified | |
236 | after a comma, it will apply to writes only. In other words, | |
237 | the format is either bs=read_and_write or bs=read,write. | |
238 | bs=4k,8k will thus use 4k blocks for reads, and 8k blocks | |
787f7e95 JA |
239 | for writes. If you only wish to set the write size, you |
240 | can do so by passing an empty read size - bs=,8k will set | |
241 | 8k for writes and leave the read default value. | |
a00735e6 | 242 | |
71bfa161 JA |
243 | bsrange=irange Instead of giving a single block size, specify a range |
244 | and fio will mix the issued io block sizes. The issued | |
245 | io unit will always be a multiple of the minimum value | |
f90eff5a JA |
246 | given (also see bs_unaligned). Applies to both reads and |
247 | writes, however a second range can be given after a comma. | |
248 | See bs=. | |
a00735e6 | 249 | |
690adba3 JA |
250 | bs_unaligned If this option is given, any byte size value within bsrange |
251 | may be used as a block range. This typically wont work with | |
252 | direct IO, as that normally requires sector alignment. | |
71bfa161 JA |
253 | |
254 | nrfiles=int Number of files to use for this job. Defaults to 1. | |
255 | ||
5af1c6f3 JA |
256 | file_service_type=str Defines how fio decides which file from a job to |
257 | service next. The following types are defined: | |
258 | ||
259 | random Just choose a file at random. | |
260 | ||
261 | roundrobin Round robin over open files. This | |
262 | is the default. | |
263 | ||
71bfa161 JA |
264 | ioengine=str Defines how the job issues io to the file. The following |
265 | types are defined: | |
266 | ||
267 | sync Basic read(2) or write(2) io. lseek(2) is | |
268 | used to position the io location. | |
269 | ||
270 | libaio Linux native asynchronous io. | |
271 | ||
272 | posixaio glibc posix asynchronous io. | |
273 | ||
274 | mmap File is memory mapped and data copied | |
275 | to/from using memcpy(3). | |
276 | ||
277 | splice splice(2) is used to transfer the data and | |
278 | vmsplice(2) to transfer data from user | |
279 | space to the kernel. | |
280 | ||
d0ff85df JA |
281 | syslet-rw Use the syslet system calls to make |
282 | regular read/write async. | |
283 | ||
71bfa161 | 284 | sg SCSI generic sg v3 io. May either be |
6c219763 | 285 | synchronous using the SG_IO ioctl, or if |
71bfa161 JA |
286 | the target is an sg character device |
287 | we use read(2) and write(2) for asynchronous | |
288 | io. | |
289 | ||
a94ea28b JA |
290 | null Doesn't transfer any data, just pretends |
291 | to. This is mainly used to exercise fio | |
292 | itself and for debugging/testing purposes. | |
293 | ||
ed92ac0c JA |
294 | net Transfer over the network to given host:port. |
295 | 'filename' must be set appropriately to | |
296 | filename=host:port regardless of send | |
297 | or receive, if the latter only the port | |
298 | argument is used. | |
299 | ||
8a7bd877 JA |
300 | external Prefix to specify loading an external |
301 | IO engine object file. Append the engine | |
302 | filename, eg ioengine=external:/tmp/foo.o | |
303 | to load ioengine foo.o in /tmp. | |
304 | ||
71bfa161 JA |
305 | iodepth=int This defines how many io units to keep in flight against |
306 | the file. The default is 1 for each file defined in this | |
307 | job, can be overridden with a larger value for higher | |
308 | concurrency. | |
309 | ||
cb5ab512 JA |
310 | iodepth_batch=int This defines how many pieces of IO to submit at once. |
311 | It defaults to the same as iodepth, but can be set lower | |
312 | if one so desires. | |
313 | ||
e916b390 JA |
314 | iodepth_low=int The low water mark indicating when to start filling |
315 | the queue again. Defaults to the same as iodepth, meaning | |
316 | that fio will attempt to keep the queue full at all times. | |
317 | If iodepth is set to eg 16 and iodepth_low is set to 4, then | |
318 | after fio has filled the queue of 16 requests, it will let | |
319 | the depth drain down to 4 before starting to fill it again. | |
320 | ||
71bfa161 | 321 | direct=bool If value is true, use non-buffered io. This is usually |
76a43db4 JA |
322 | O_DIRECT. |
323 | ||
324 | buffered=bool If value is true, use buffered io. This is the opposite | |
325 | of the 'direct' option. Defaults to true. | |
71bfa161 JA |
326 | |
327 | offset=siint Start io at the given offset in the file. The data before | |
328 | the given offset will not be touched. This effectively | |
329 | caps the file size at real_size - offset. | |
330 | ||
331 | fsync=int If writing to a file, issue a sync of the dirty data | |
332 | for every number of blocks given. For example, if you give | |
333 | 32 as a parameter, fio will sync the file for every 32 | |
334 | writes issued. If fio is using non-buffered io, we may | |
335 | not sync the file. The exception is the sg io engine, which | |
6c219763 | 336 | synchronizes the disk cache anyway. |
71bfa161 JA |
337 | |
338 | overwrite=bool If writing to a file, setup the file first and do overwrites. | |
339 | ||
340 | end_fsync=bool If true, fsync file contents when the job exits. | |
341 | ||
6c219763 | 342 | rwmixcycle=int Value in milliseconds describing how often to switch between |
71bfa161 JA |
343 | reads and writes for a mixed workload. The default is |
344 | 500 msecs. | |
345 | ||
346 | rwmixread=int How large a percentage of the mix should be reads. | |
347 | ||
348 | rwmixwrite=int How large a percentage of the mix should be writes. If both | |
349 | rwmixread and rwmixwrite is given and the values do not add | |
350 | up to 100%, the latter of the two will be used to override | |
351 | the first. | |
352 | ||
bb8895e0 JA |
353 | norandommap Normally fio will cover every block of the file when doing |
354 | random IO. If this option is given, fio will just get a | |
355 | new random offset without looking at past io history. This | |
356 | means that some blocks may not be read or written, and that | |
357 | some blocks may be read/written more than once. This option | |
358 | is mutually exclusive with verify= for that reason. | |
359 | ||
71bfa161 JA |
360 | nice=int Run the job with the given nice value. See man nice(2). |
361 | ||
362 | prio=int Set the io priority value of this job. Linux limits us to | |
363 | a positive value between 0 and 7, with 0 being the highest. | |
364 | See man ionice(1). | |
365 | ||
366 | prioclass=int Set the io priority class. See man ionice(1). | |
367 | ||
368 | thinktime=int Stall the job x microseconds after an io has completed before | |
369 | issuing the next. May be used to simulate processing being | |
48097d5c JA |
370 | done by an application. See thinktime_blocks and |
371 | thinktime_spin. | |
372 | ||
373 | thinktime_spin=int | |
374 | Only valid if thinktime is set - pretend to spend CPU time | |
375 | doing something with the data received, before falling back | |
376 | to sleeping for the rest of the period specified by | |
377 | thinktime. | |
9c1f7434 JA |
378 | |
379 | thinktime_blocks | |
380 | Only valid if thinktime is set - control how many blocks | |
381 | to issue, before waiting 'thinktime' usecs. If not set, | |
382 | defaults to 1 which will make fio wait 'thinktime' usecs | |
383 | after every block. | |
71bfa161 JA |
384 | |
385 | rate=int Cap the bandwidth used by this job to this number of KiB/sec. | |
386 | ||
387 | ratemin=int Tell fio to do whatever it can to maintain at least this | |
388 | bandwidth. | |
389 | ||
390 | ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number | |
6c219763 | 391 | of milliseconds. |
71bfa161 JA |
392 | |
393 | cpumask=int Set the CPU affinity of this job. The parameter given is a | |
394 | bitmask of allowed CPU's the job may run on. See man | |
395 | sched_setaffinity(2). | |
396 | ||
397 | startdelay=int Start this job the specified number of seconds after fio | |
398 | has started. Only useful if the job file contains several | |
399 | jobs, and you want to delay starting some jobs to a certain | |
400 | time. | |
401 | ||
03b74b3e | 402 | runtime=int Tell fio to terminate processing after the specified number |
71bfa161 JA |
403 | of seconds. It can be quite hard to determine for how long |
404 | a specified job will run, so this parameter is handy to | |
405 | cap the total runtime to a given time. | |
406 | ||
407 | invalidate=bool Invalidate the buffer/page cache parts for this file prior | |
408 | to starting io. Defaults to true. | |
409 | ||
410 | sync=bool Use sync io for buffered writes. For the majority of the | |
411 | io engines, this means using O_SYNC. | |
412 | ||
413 | mem=str Fio can use various types of memory as the io unit buffer. | |
414 | The allowed values are: | |
415 | ||
416 | malloc Use memory from malloc(3) as the buffers. | |
417 | ||
418 | shm Use shared memory as the buffers. Allocated | |
419 | through shmget(2). | |
420 | ||
74b025b0 JA |
421 | shmhuge Same as shm, but use huge pages as backing. |
422 | ||
313cb206 JA |
423 | mmap Use mmap to allocate buffers. May either be |
424 | anonymous memory, or can be file backed if | |
425 | a filename is given after the option. The | |
426 | format is mem=mmap:/path/to/file. | |
71bfa161 | 427 | |
d0bdaf49 JA |
428 | mmaphuge Use a memory mapped huge file as the buffer |
429 | backing. Append filename after mmaphuge, ala | |
430 | mem=mmaphuge:/hugetlbfs/file | |
431 | ||
71bfa161 | 432 | The area allocated is a function of the maximum allowed |
5394ae5f JA |
433 | bs size for the job, multiplied by the io depth given. Note |
434 | that for shmhuge and mmaphuge to work, the system must have | |
435 | free huge pages allocated. This can normally be checked | |
436 | and set by reading/writing /proc/sys/vm/nr_hugepages on a | |
437 | Linux system. Fio assumes a huge page is 4MiB in size. So | |
438 | to calculate the number of huge pages you need for a given | |
439 | job file, add up the io depth of all jobs (normally one unless | |
440 | iodepth= is used) and multiply by the maximum bs set. Then | |
441 | divide that number by the huge page size. You can see the | |
442 | size of the huge pages in /proc/meminfo. If no huge pages | |
443 | are allocated by having a non-zero number in nr_hugepages, | |
56bb17f2 | 444 | using mmaphuge or shmhuge will fail. Also see hugepage-size. |
5394ae5f JA |
445 | |
446 | mmaphuge also needs to have hugetlbfs mounted and the file | |
447 | location should point there. So if it's mounted in /huge, | |
448 | you would use mem=mmaphuge:/huge/somefile. | |
71bfa161 | 449 | |
56bb17f2 JA |
450 | hugepage-size=siint |
451 | Defines the size of a huge page. Must at least be equal | |
452 | to the system setting, see /proc/meminfo. Defaults to 4MiB. | |
c51074e7 JA |
453 | Should probably always be a multiple of megabytes, so using |
454 | hugepage-size=Xm is the preferred way to set this to avoid | |
455 | setting a non-pow-2 bad value. | |
56bb17f2 | 456 | |
71bfa161 JA |
457 | exitall When one job finishes, terminate the rest. The default is |
458 | to wait for each job to finish, sometimes that is not the | |
459 | desired action. | |
460 | ||
461 | bwavgtime=int Average the calculated bandwidth over the given time. Value | |
6c219763 | 462 | is specified in milliseconds. |
71bfa161 JA |
463 | |
464 | create_serialize=bool If true, serialize the file creating for the jobs. | |
465 | This may be handy to avoid interleaving of data | |
466 | files, which may greatly depend on the filesystem | |
467 | used and even the number of processors in the system. | |
468 | ||
469 | create_fsync=bool fsync the data file after creation. This is the | |
470 | default. | |
471 | ||
e545a6ce JA |
472 | unlink=bool Unlink the job files when done. Not the default, as repeated |
473 | runs of that job would then waste time recreating the fileset | |
474 | again and again. | |
71bfa161 JA |
475 | |
476 | loops=int Run the specified number of iterations of this job. Used | |
477 | to repeat the same workload a given number of times. Defaults | |
478 | to 1. | |
479 | ||
480 | verify=str If writing to a file, fio can verify the file contents | |
481 | after each iteration of the job. The allowed values are: | |
482 | ||
483 | md5 Use an md5 sum of the data area and store | |
484 | it in the header of each block. | |
485 | ||
486 | crc32 Use a crc32 sum of the data area and store | |
487 | it in the header of each block. | |
488 | ||
6c219763 | 489 | This option can be used for repeated burn-in tests of a |
71bfa161 JA |
490 | system to make sure that the written data is also |
491 | correctly read back. | |
492 | ||
493 | stonewall Wait for preceeding jobs in the job file to exit, before | |
494 | starting this one. Can be used to insert serialization | |
495 | points in the job file. | |
496 | ||
497 | numjobs=int Create the specified number of clones of this job. May be | |
498 | used to setup a larger number of threads/processes doing | |
fa28c85a JA |
499 | the same thing. We regard that grouping of jobs as a |
500 | specific group. | |
501 | ||
502 | group_reporting If 'numjobs' is set, it may be interesting to display | |
503 | statistics for the group as a whole instead of for each | |
504 | individual job. This is especially true of 'numjobs' is | |
505 | large, looking at individual thread/process output quickly | |
506 | becomes unwieldy. If 'group_reporting' is specified, fio | |
507 | will show the final report per-group instead of per-job. | |
71bfa161 JA |
508 | |
509 | thread fio defaults to forking jobs, however if this option is | |
510 | given, fio will use pthread_create(3) to create threads | |
511 | instead. | |
512 | ||
513 | zonesize=siint Divide a file into zones of the specified size. See zoneskip. | |
514 | ||
515 | zoneskip=siint Skip the specified number of bytes when zonesize data has | |
516 | been read. The two zone options can be used to only do | |
517 | io on zones of a file. | |
518 | ||
076efc7c JA |
519 | write_iolog=str Write the issued io patterns to the specified file. See |
520 | read_iolog. | |
71bfa161 | 521 | |
076efc7c | 522 | read_iolog=str Open an iolog with the specified file name and replay the |
71bfa161 JA |
523 | io patterns it contains. This can be used to store a |
524 | workload and replay it sometime later. | |
525 | ||
526 | write_bw_log If given, write a bandwidth log of the jobs in this job | |
527 | file. Can be used to store data of the bandwidth of the | |
e0da9bc2 JA |
528 | jobs in their lifetime. The included fio_generate_plots |
529 | script uses gnuplot to turn these text files into nice | |
530 | graphs. | |
71bfa161 JA |
531 | |
532 | write_lat_log Same as write_bw_log, except that this option stores io | |
533 | completion latencies instead. | |
534 | ||
535 | lockmem=siint Pin down the specified amount of memory with mlock(2). Can | |
536 | potentially be used instead of removing memory or booting | |
537 | with less memory to simulate a smaller amount of memory. | |
538 | ||
539 | exec_prerun=str Before running this job, issue the command specified | |
540 | through system(3). | |
541 | ||
542 | exec_postrun=str After the job completes, issue the command specified | |
543 | though system(3). | |
544 | ||
545 | ioscheduler=str Attempt to switch the device hosting the file to the specified | |
546 | io scheduler before running. | |
547 | ||
548 | cpuload=int If the job is a CPU cycle eater, attempt to use the specified | |
549 | percentage of CPU cycles. | |
550 | ||
551 | cpuchunks=int If the job is a CPU cycle eater, split the load into | |
6c219763 | 552 | cycles of the given time. In milliseconds. |
71bfa161 JA |
553 | |
554 | ||
555 | 6.0 Interpreting the output | |
556 | --------------------------- | |
557 | ||
558 | fio spits out a lot of output. While running, fio will display the | |
559 | status of the jobs created. An example of that would be: | |
560 | ||
73c8b082 | 561 | Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] |
71bfa161 JA |
562 | |
563 | The characters inside the square brackets denote the current status of | |
564 | each thread. The possible values (in typical life cycle order) are: | |
565 | ||
566 | Idle Run | |
567 | ---- --- | |
568 | P Thread setup, but not started. | |
569 | C Thread created. | |
570 | I Thread initialized, waiting. | |
571 | R Running, doing sequential reads. | |
572 | r Running, doing random reads. | |
573 | W Running, doing sequential writes. | |
574 | w Running, doing random writes. | |
575 | M Running, doing mixed sequential reads/writes. | |
576 | m Running, doing mixed random reads/writes. | |
577 | F Running, currently waiting for fsync() | |
578 | V Running, doing verification of written data. | |
579 | E Thread exited, not reaped by main thread yet. | |
580 | _ Thread reaped. | |
581 | ||
582 | The other values are fairly self explanatory - number of threads | |
6043c579 JA |
583 | currently running and doing io, rate of io since last check, and the estimated |
584 | completion percentage and time for the running group. It's impossible to | |
585 | estimate runtime of the following groups (if any). | |
71bfa161 JA |
586 | |
587 | When fio is done (or interrupted by ctrl-c), it will show the data for | |
588 | each thread, group of threads, and disks in that order. For each data | |
589 | direction, the output looks like: | |
590 | ||
591 | Client1 (g=0): err= 0: | |
592 | write: io= 32MiB, bw= 666KiB/s, runt= 50320msec | |
6104ddb6 JA |
593 | slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92 |
594 | clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82 | |
595 | bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68 | |
71bfa161 | 596 | cpu : usr=1.49%, sys=0.25%, ctx=7969 |
71619dc2 | 597 | IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% |
8abdce66 JA |
598 | lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%, |
599 | lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0% | |
71bfa161 JA |
600 | |
601 | The client number is printed, along with the group id and error of that | |
602 | thread. Below is the io statistics, here for writes. In the order listed, | |
603 | they denote: | |
604 | ||
605 | io= Number of megabytes io performed | |
606 | bw= Average bandwidth rate | |
607 | runt= The runtime of that thread | |
608 | slat= Submission latency (avg being the average, dev being the | |
609 | standard deviation). This is the time it took to submit | |
610 | the io. For sync io, the slat is really the completion | |
611 | latency, since queue/complete is one operation there. | |
612 | clat= Completion latency. Same names as slat, this denotes the | |
613 | time from submission to completion of the io pieces. For | |
614 | sync io, clat will usually be equal (or very close) to 0, | |
615 | as the time from submit to complete is basically just | |
616 | CPU time (io has already been done, see slat explanation). | |
617 | bw= Bandwidth. Same names as the xlat stats, but also includes | |
618 | an approximate percentage of total aggregate bandwidth | |
619 | this thread received in this group. This last value is | |
620 | only really useful if the threads in this group are on the | |
621 | same disk, since they are then competing for disk access. | |
622 | cpu= CPU usage. User and system time, along with the number | |
623 | of context switches this thread went through. | |
71619dc2 JA |
624 | IO depths= The distribution of io depths over the job life time. The |
625 | numbers are divided into powers of 2, so for example the | |
626 | 16= entries includes depths up to that value but higher | |
627 | than the previous entry. In other words, it covers the | |
628 | range from 16 to 31. | |
ec118304 JA |
629 | IO latencies= The distribution of IO completion latencies. This is the |
630 | time from when IO leaves fio and when it gets completed. | |
631 | The numbers follow the same pattern as the IO depths, | |
632 | meaning that 2=1.6% means that 1.6% of the IO completed | |
8abdce66 JA |
633 | within 2 msecs, 20=12.8% means that 12.8% of the IO |
634 | took more than 10 msecs, but less than (or equal to) 20 msecs. | |
71bfa161 JA |
635 | |
636 | After each client has been listed, the group statistics are printed. They | |
637 | will look like this: | |
638 | ||
639 | Run status group 0 (all jobs): | |
640 | READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec | |
641 | WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec | |
642 | ||
643 | For each data direction, it prints: | |
644 | ||
645 | io= Number of megabytes io performed. | |
646 | aggrb= Aggregate bandwidth of threads in this group. | |
647 | minb= The minimum average bandwidth a thread saw. | |
648 | maxb= The maximum average bandwidth a thread saw. | |
649 | mint= The smallest runtime of the threads in that group. | |
650 | maxt= The longest runtime of the threads in that group. | |
651 | ||
652 | And finally, the disk statistics are printed. They will look like this: | |
653 | ||
654 | Disk stats (read/write): | |
655 | sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00% | |
656 | ||
657 | Each value is printed for both reads and writes, with reads first. The | |
658 | numbers denote: | |
659 | ||
660 | ios= Number of ios performed by all groups. | |
661 | merge= Number of merges io the io scheduler. | |
662 | ticks= Number of ticks we kept the disk busy. | |
663 | io_queue= Total time spent in the disk queue. | |
664 | util= The disk utilization. A value of 100% means we kept the disk | |
665 | busy constantly, 50% would be a disk idling half of the time. | |
666 | ||
667 | ||
668 | 7.0 Terse output | |
669 | ---------------- | |
670 | ||
671 | For scripted usage where you typically want to generate tables or graphs | |
6c219763 | 672 | of the results, fio can output the results in a comma separated format. |
71bfa161 JA |
673 | The format is one long line of values, such as: |
674 | ||
675 | client1,0,0,936,331,2894,0,0,0.000000,0.000000,1,170,22.115385,34.290410,16,714,84.252874%,366.500000,566.417819,3496,1237,2894,0,0,0.000000,0.000000,0,246,6.671625,21.436952,0,2534,55.465300%,1406.600000,2008.044216,0.000000%,0.431928%,1109 | |
676 | ||
677 | Split up, the format is as follows: | |
678 | ||
679 | jobname, groupid, error | |
680 | READ status: | |
681 | KiB IO, bandwidth (KiB/sec), runtime (msec) | |
682 | Submission latency: min, max, mean, deviation | |
683 | Completion latency: min, max, mean, deviation | |
6c219763 | 684 | Bw: min, max, aggregate percentage of total, mean, deviation |
71bfa161 JA |
685 | WRITE status: |
686 | KiB IO, bandwidth (KiB/sec), runtime (msec) | |
687 | Submission latency: min, max, mean, deviation | |
688 | Completion latency: min, max, mean, deviation | |
6c219763 | 689 | Bw: min, max, aggregate percentage of total, mean, deviation |
71bfa161 | 690 | CPU usage: user, system, context switches |
2270890c JA |
691 | IO depths: <=1, 2, 4, 8, 16, 32, >=64 |
692 | IO latencies: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000 | |
693 | Text description | |
71bfa161 | 694 |