'new_group' option
[fio.git] / HOWTO
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1Table of contents
2-----------------
3
41. Overview
52. How fio works
63. Running fio
74. Job file format
85. Detailed list of parameters
96. Normal output
107. Terse output
11
12
131.0 Overview and history
14------------------------
15fio was originally written to save me the hassle of writing special test
16case programs when I wanted to test a specific workload, either for
17performance reasons or to find/reproduce a bug. The process of writing
18such a test app can be tiresome, especially if you have to do it often.
19Hence I needed a tool that would be able to simulate a given io workload
20without resorting to writing a tailored test case again and again.
21
22A test work load is difficult to define, though. There can be any number
23of processes or threads involved, and they can each be using their own
24way of generating io. You could have someone dirtying large amounts of
25memory in an memory mapped file, or maybe several threads issuing
26reads using asynchronous io. fio needed to be flexible enough to
27simulate both of these cases, and many more.
28
292.0 How fio works
30-----------------
31The first step in getting fio to simulate a desired io workload, is
32writing a job file describing that specific setup. A job file may contain
33any number of threads and/or files - the typical contents of the job file
34is a global section defining shared parameters, and one or more job
35sections describing the jobs involved. When run, fio parses this file
36and sets everything up as described. If we break down a job from top to
37bottom, 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
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53 SG (SCSI generic sg).
54
6c219763 55 IO depth If the io engine is async, how large a queuing
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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
65The above are the basic parameters defined for a workload, in addition
66there's a multitude of parameters that modify other aspects of how this
67job behaves.
68
69
703.0 Running fio
71---------------
72See the README file for command line parameters, there are only a few
73of them.
74
75Running 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
80and it will start doing what the job_file tells it to do. You can give
81more than one job file on the command line, fio will serialize the running
82of those files. Internally that is the same as using the 'stonewall'
83parameter described the the parameter section.
84
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85If the job file contains only one job, you may as well just give the
86parameters on the command line. The command line parameters are identical
87to the job parameters, with a few extra that control global parameters
88(see README). For example, for the job file parameter iodepth=2, the
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89mirror command line option would be --iodepth 2 or --iodepth=2. You can
90also 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.
92Command line entries following a --name entry will apply to that job,
93until there are no more entries or a new --name entry is seen. This is
94similar to the job file options, where each option applies to the current
95job until a new [] job entry is seen.
b4692828 96
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97fio does not need to run as root, except if the files or devices specified
98in the job section requires that. Some other options may also be restricted,
6c219763 99such as memory locking, io scheduler switching, and decreasing the nice value.
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100
101
1024.0 Job file format
103-------------------
104As previously described, fio accepts one or more job files describing
105what it is supposed to do. The job file format is the classic ini file,
106where the names enclosed in [] brackets define the job name. You are free
107to use any ascii name you want, except 'global' which has special meaning.
108A global section sets defaults for the jobs described in that file. A job
109may override a global section parameter, and a job file may even have
110several global sections if so desired. A job is only affected by a global
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111section residing above it. If the first character in a line is a ';' or a
112'#', the entire line is discarded as a comment.
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113
114So lets look at a really simple job file that define to threads, each
115randomly reading from a 128MiB file.
116
117; -- start job file --
118[global]
119rw=randread
120size=128m
121
122[job1]
123
124[job2]
125
126; -- end job file --
127
128As you can see, the job file sections themselves are empty as all the
129described parameters are shared. As no filename= option is given, fio
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130makes up a filename for each of the jobs as it sees fit. On the command
131line, this job would look as follows:
132
133$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
134
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135
136Lets look at an example that have a number of processes writing randomly
137to files.
138
139; -- start job file --
140[random-writers]
141ioengine=libaio
142iodepth=4
143rw=randwrite
144bs=32k
145direct=0
146size=64m
147numjobs=4
148
149; -- end job file --
150
151Here we have no global section, as we only have one job defined anyway.
152We want to use async io here, with a depth of 4 for each file. We also
153increased the buffer size used to 32KiB and define numjobs to 4 to
154fork 4 identical jobs. The result is 4 processes each randomly writing
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155to their own 64MiB file. Instead of using the above job file, you could
156have given the parameters on the command line. For this case, you would
157specify:
158
159$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
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160
161fio ships with a few example job files, you can also look there for
162inspiration.
163
164
1655.0 Detailed list of parameters
166-------------------------------
167
168This section describes in details each parameter associated with a job.
169Some parameters take an option of a given type, such as an integer or
170a string. The following types are used:
171
172str String. This is a sequence of alpha characters.
173int Integer. A whole number value, may be negative.
174siint 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,
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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.
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179 If the option accepts an upper and lower range, use a colon ':'
180 or minus '-' to seperate such values. See irange.
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181bool Boolean. Usually parsed as an integer, however only defined for
182 true and false (1 and 0).
183irange Integer range with postfix. Allows value range to be given, such
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184 as 1024-4096. A colon may also be used as the seperator, eg
185 1k:4k. If the option allows two sets of ranges, they can be
186 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
187 siint.
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188
189With the above in mind, here follows the complete list of fio job
190parameters.
191
192name=str ASCII name of the job. This may be used to override the
193 name printed by fio for this job. Otherwise the job
c2b1e753 194 name is used. On the command line this parameter has the
6c219763 195 special purpose of also signaling the start of a new
c2b1e753 196 job.
71bfa161 197
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198description=str Text description of the job. Doesn't do anything except
199 dump this text description when this job is run. It's
200 not parsed.
201
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202directory=str Prefix filenames with this directory. Used to places files
203 in a different location than "./".
204
205filename=str Fio normally makes up a filename based on the job name,
206 thread number, and file number. If you want to share
207 files between threads in a job or several jobs, specify
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208 a filename for each of them to override the default. If
209 the ioengine used is 'net', the filename is the host and
9f9214f2 210 port to connect to in the format of =host/port. If the
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211 ioengine is file based, you can specify a number of files
212 by seperating the names with a ':' colon. So if you wanted
213 a job to open /dev/sda and /dev/sdb as the two working files,
214 you would use filename=/dev/sda:/dev/sdb
71bfa161 215
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216opendir=str Tell fio to recursively add any file it can find in this
217 directory and down the file system tree.
218
d3aad8f2 219readwrite=str
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220rw=str Type of io pattern. Accepted values are:
221
222 read Sequential reads
223 write Sequential writes
224 randwrite Random writes
225 randread Random reads
226 rw Sequential mixed reads and writes
227 randrw Random mixed reads and writes
228
229 For the mixed io types, the default is to split them 50/50.
230 For certain types of io the result may still be skewed a bit,
231 since the speed may be different.
232
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233randrepeat=bool For random IO workloads, seed the generator in a predictable
234 way so that results are repeatable across repetitions.
235
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236size=siint The total size of file io for this job. This may describe
237 the size of the single file the job uses, or it may be
238 divided between the number of files in the job. If the
239 file already exists, the file size will be adjusted to this
240 size if larger than the current file size. If this parameter
241 is not given and the file exists, the file size will be used.
242
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243filesize=siint Individual file sizes. May be a range, in which case fio
244 will select sizes for files at random within the given range
245 and limited to 'size' in total (if that is given). If not
246 given, each created file is the same size.
247
d3aad8f2 248blocksize=siint
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249bs=siint The block size used for the io units. Defaults to 4k. Values
250 can be given for both read and writes. If a single siint is
251 given, it will apply to both. If a second siint is specified
252 after a comma, it will apply to writes only. In other words,
253 the format is either bs=read_and_write or bs=read,write.
254 bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
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255 for writes. If you only wish to set the write size, you
256 can do so by passing an empty read size - bs=,8k will set
257 8k for writes and leave the read default value.
a00735e6 258
d3aad8f2 259blocksize_range=irange
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260bsrange=irange Instead of giving a single block size, specify a range
261 and fio will mix the issued io block sizes. The issued
262 io unit will always be a multiple of the minimum value
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263 given (also see bs_unaligned). Applies to both reads and
264 writes, however a second range can be given after a comma.
265 See bs=.
a00735e6 266
d3aad8f2 267blocksize_unaligned
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268bs_unaligned If this option is given, any byte size value within bsrange
269 may be used as a block range. This typically wont work with
270 direct IO, as that normally requires sector alignment.
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271
272nrfiles=int Number of files to use for this job. Defaults to 1.
273
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274openfiles=int Number of files to keep open at the same time. Defaults to
275 the same as nrfiles, can be set smaller to limit the number
276 simultaneous opens.
277
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278file_service_type=str Defines how fio decides which file from a job to
279 service next. The following types are defined:
280
281 random Just choose a file at random.
282
283 roundrobin Round robin over open files. This
284 is the default.
285
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286 The string can have a number appended, indicating how
287 often to switch to a new file. So if option random:4 is
288 given, fio will switch to a new random file after 4 ios
289 have been issued.
290
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291ioengine=str Defines how the job issues io to the file. The following
292 types are defined:
293
294 sync Basic read(2) or write(2) io. lseek(2) is
295 used to position the io location.
296
297 libaio Linux native asynchronous io.
298
299 posixaio glibc posix asynchronous io.
300
301 mmap File is memory mapped and data copied
302 to/from using memcpy(3).
303
304 splice splice(2) is used to transfer the data and
305 vmsplice(2) to transfer data from user
306 space to the kernel.
307
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308 syslet-rw Use the syslet system calls to make
309 regular read/write async.
310
71bfa161 311 sg SCSI generic sg v3 io. May either be
6c219763 312 synchronous using the SG_IO ioctl, or if
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313 the target is an sg character device
314 we use read(2) and write(2) for asynchronous
315 io.
316
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317 null Doesn't transfer any data, just pretends
318 to. This is mainly used to exercise fio
319 itself and for debugging/testing purposes.
320
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321 net Transfer over the network to given host:port.
322 'filename' must be set appropriately to
9f9214f2 323 filename=host/port regardless of send
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324 or receive, if the latter only the port
325 argument is used.
326
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327 cpu Doesn't transfer any data, but burns CPU
328 cycles according to the cpuload= and
329 cpucycle= options. Setting cpuload=85
330 will cause that job to do nothing but burn
331 85% of the CPU.
332
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333 external Prefix to specify loading an external
334 IO engine object file. Append the engine
335 filename, eg ioengine=external:/tmp/foo.o
336 to load ioengine foo.o in /tmp.
337
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338iodepth=int This defines how many io units to keep in flight against
339 the file. The default is 1 for each file defined in this
340 job, can be overridden with a larger value for higher
341 concurrency.
342
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343iodepth_batch=int This defines how many pieces of IO to submit at once.
344 It defaults to the same as iodepth, but can be set lower
345 if one so desires.
346
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347iodepth_low=int The low water mark indicating when to start filling
348 the queue again. Defaults to the same as iodepth, meaning
349 that fio will attempt to keep the queue full at all times.
350 If iodepth is set to eg 16 and iodepth_low is set to 4, then
351 after fio has filled the queue of 16 requests, it will let
352 the depth drain down to 4 before starting to fill it again.
353
71bfa161 354direct=bool If value is true, use non-buffered io. This is usually
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355 O_DIRECT.
356
357buffered=bool If value is true, use buffered io. This is the opposite
358 of the 'direct' option. Defaults to true.
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359
360offset=siint Start io at the given offset in the file. The data before
361 the given offset will not be touched. This effectively
362 caps the file size at real_size - offset.
363
364fsync=int If writing to a file, issue a sync of the dirty data
365 for every number of blocks given. For example, if you give
366 32 as a parameter, fio will sync the file for every 32
367 writes issued. If fio is using non-buffered io, we may
368 not sync the file. The exception is the sg io engine, which
6c219763 369 synchronizes the disk cache anyway.
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370
371overwrite=bool If writing to a file, setup the file first and do overwrites.
372
373end_fsync=bool If true, fsync file contents when the job exits.
374
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375fsync_on_close=bool If true, fio will fsync() a dirty file on close.
376 This differs from end_fsync in that it will happen on every
377 file close, not just at the end of the job.
378
6c219763 379rwmixcycle=int Value in milliseconds describing how often to switch between
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380 reads and writes for a mixed workload. The default is
381 500 msecs.
382
383rwmixread=int How large a percentage of the mix should be reads.
384
385rwmixwrite=int How large a percentage of the mix should be writes. If both
386 rwmixread and rwmixwrite is given and the values do not add
387 up to 100%, the latter of the two will be used to override
388 the first.
389
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390norandommap Normally fio will cover every block of the file when doing
391 random IO. If this option is given, fio will just get a
392 new random offset without looking at past io history. This
393 means that some blocks may not be read or written, and that
394 some blocks may be read/written more than once. This option
395 is mutually exclusive with verify= for that reason.
396
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397nice=int Run the job with the given nice value. See man nice(2).
398
399prio=int Set the io priority value of this job. Linux limits us to
400 a positive value between 0 and 7, with 0 being the highest.
401 See man ionice(1).
402
403prioclass=int Set the io priority class. See man ionice(1).
404
405thinktime=int Stall the job x microseconds after an io has completed before
406 issuing the next. May be used to simulate processing being
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407 done by an application. See thinktime_blocks and
408 thinktime_spin.
409
410thinktime_spin=int
411 Only valid if thinktime is set - pretend to spend CPU time
412 doing something with the data received, before falling back
413 to sleeping for the rest of the period specified by
414 thinktime.
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415
416thinktime_blocks
417 Only valid if thinktime is set - control how many blocks
418 to issue, before waiting 'thinktime' usecs. If not set,
419 defaults to 1 which will make fio wait 'thinktime' usecs
420 after every block.
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421
422rate=int Cap the bandwidth used by this job to this number of KiB/sec.
423
424ratemin=int Tell fio to do whatever it can to maintain at least this
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425 bandwidth. Failing to meet this requirement, will cause
426 the job to exit.
427
428rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
429 as rate, just specified independently of bandwidth. If the
430 job is given a block size range instead of a fixed value,
431 the smallest block size is used as the metric.
432
433rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
434 the job to exit.
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435
436ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number
6c219763 437 of milliseconds.
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438
439cpumask=int Set the CPU affinity of this job. The parameter given is a
440 bitmask of allowed CPU's the job may run on. See man
441 sched_setaffinity(2).
442
443startdelay=int Start this job the specified number of seconds after fio
444 has started. Only useful if the job file contains several
445 jobs, and you want to delay starting some jobs to a certain
446 time.
447
03b74b3e 448runtime=int Tell fio to terminate processing after the specified number
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449 of seconds. It can be quite hard to determine for how long
450 a specified job will run, so this parameter is handy to
451 cap the total runtime to a given time.
452
453invalidate=bool Invalidate the buffer/page cache parts for this file prior
454 to starting io. Defaults to true.
455
456sync=bool Use sync io for buffered writes. For the majority of the
457 io engines, this means using O_SYNC.
458
d3aad8f2 459iomem=str
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460mem=str Fio can use various types of memory as the io unit buffer.
461 The allowed values are:
462
463 malloc Use memory from malloc(3) as the buffers.
464
465 shm Use shared memory as the buffers. Allocated
466 through shmget(2).
467
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468 shmhuge Same as shm, but use huge pages as backing.
469
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470 mmap Use mmap to allocate buffers. May either be
471 anonymous memory, or can be file backed if
472 a filename is given after the option. The
473 format is mem=mmap:/path/to/file.
71bfa161 474
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475 mmaphuge Use a memory mapped huge file as the buffer
476 backing. Append filename after mmaphuge, ala
477 mem=mmaphuge:/hugetlbfs/file
478
71bfa161 479 The area allocated is a function of the maximum allowed
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480 bs size for the job, multiplied by the io depth given. Note
481 that for shmhuge and mmaphuge to work, the system must have
482 free huge pages allocated. This can normally be checked
483 and set by reading/writing /proc/sys/vm/nr_hugepages on a
484 Linux system. Fio assumes a huge page is 4MiB in size. So
485 to calculate the number of huge pages you need for a given
486 job file, add up the io depth of all jobs (normally one unless
487 iodepth= is used) and multiply by the maximum bs set. Then
488 divide that number by the huge page size. You can see the
489 size of the huge pages in /proc/meminfo. If no huge pages
490 are allocated by having a non-zero number in nr_hugepages,
56bb17f2 491 using mmaphuge or shmhuge will fail. Also see hugepage-size.
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492
493 mmaphuge also needs to have hugetlbfs mounted and the file
494 location should point there. So if it's mounted in /huge,
495 you would use mem=mmaphuge:/huge/somefile.
71bfa161 496
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497hugepage-size=siint
498 Defines the size of a huge page. Must at least be equal
499 to the system setting, see /proc/meminfo. Defaults to 4MiB.
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500 Should probably always be a multiple of megabytes, so using
501 hugepage-size=Xm is the preferred way to set this to avoid
502 setting a non-pow-2 bad value.
56bb17f2 503
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504exitall When one job finishes, terminate the rest. The default is
505 to wait for each job to finish, sometimes that is not the
506 desired action.
507
508bwavgtime=int Average the calculated bandwidth over the given time. Value
6c219763 509 is specified in milliseconds.
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510
511create_serialize=bool If true, serialize the file creating for the jobs.
512 This may be handy to avoid interleaving of data
513 files, which may greatly depend on the filesystem
514 used and even the number of processors in the system.
515
516create_fsync=bool fsync the data file after creation. This is the
517 default.
518
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519unlink=bool Unlink the job files when done. Not the default, as repeated
520 runs of that job would then waste time recreating the fileset
521 again and again.
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522
523loops=int Run the specified number of iterations of this job. Used
524 to repeat the same workload a given number of times. Defaults
525 to 1.
526
527verify=str If writing to a file, fio can verify the file contents
528 after each iteration of the job. The allowed values are:
529
530 md5 Use an md5 sum of the data area and store
531 it in the header of each block.
532
533 crc32 Use a crc32 sum of the data area and store
534 it in the header of each block.
535
6c219763 536 This option can be used for repeated burn-in tests of a
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537 system to make sure that the written data is also
538 correctly read back.
539
540stonewall Wait for preceeding jobs in the job file to exit, before
541 starting this one. Can be used to insert serialization
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542 points in the job file. A stone wall also implies starting
543 a new reporting group.
544
545new_group Start a new reporting group. If this option isn't given,
546 jobs in a file will be part of the same reporting group
547 unless seperated by a stone wall (or if it's a group
548 by itself, with the numjobs option).
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549
550numjobs=int Create the specified number of clones of this job. May be
551 used to setup a larger number of threads/processes doing
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552 the same thing. We regard that grouping of jobs as a
553 specific group.
554
555group_reporting If 'numjobs' is set, it may be interesting to display
556 statistics for the group as a whole instead of for each
557 individual job. This is especially true of 'numjobs' is
558 large, looking at individual thread/process output quickly
559 becomes unwieldy. If 'group_reporting' is specified, fio
560 will show the final report per-group instead of per-job.
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561
562thread fio defaults to forking jobs, however if this option is
563 given, fio will use pthread_create(3) to create threads
564 instead.
565
566zonesize=siint Divide a file into zones of the specified size. See zoneskip.
567
568zoneskip=siint Skip the specified number of bytes when zonesize data has
569 been read. The two zone options can be used to only do
570 io on zones of a file.
571
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572write_iolog=str Write the issued io patterns to the specified file. See
573 read_iolog.
71bfa161 574
076efc7c 575read_iolog=str Open an iolog with the specified file name and replay the
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576 io patterns it contains. This can be used to store a
577 workload and replay it sometime later.
578
579write_bw_log If given, write a bandwidth log of the jobs in this job
580 file. Can be used to store data of the bandwidth of the
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581 jobs in their lifetime. The included fio_generate_plots
582 script uses gnuplot to turn these text files into nice
583 graphs.
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584
585write_lat_log Same as write_bw_log, except that this option stores io
586 completion latencies instead.
587
588lockmem=siint Pin down the specified amount of memory with mlock(2). Can
589 potentially be used instead of removing memory or booting
590 with less memory to simulate a smaller amount of memory.
591
592exec_prerun=str Before running this job, issue the command specified
593 through system(3).
594
595exec_postrun=str After the job completes, issue the command specified
596 though system(3).
597
598ioscheduler=str Attempt to switch the device hosting the file to the specified
599 io scheduler before running.
600
601cpuload=int If the job is a CPU cycle eater, attempt to use the specified
602 percentage of CPU cycles.
603
604cpuchunks=int If the job is a CPU cycle eater, split the load into
6c219763 605 cycles of the given time. In milliseconds.
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606
607
6086.0 Interpreting the output
609---------------------------
610
611fio spits out a lot of output. While running, fio will display the
612status of the jobs created. An example of that would be:
613
73c8b082 614Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
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615
616The characters inside the square brackets denote the current status of
617each thread. The possible values (in typical life cycle order) are:
618
619Idle Run
620---- ---
621P Thread setup, but not started.
622C Thread created.
623I Thread initialized, waiting.
624 R Running, doing sequential reads.
625 r Running, doing random reads.
626 W Running, doing sequential writes.
627 w Running, doing random writes.
628 M Running, doing mixed sequential reads/writes.
629 m Running, doing mixed random reads/writes.
630 F Running, currently waiting for fsync()
631V Running, doing verification of written data.
632E Thread exited, not reaped by main thread yet.
633_ Thread reaped.
634
635The other values are fairly self explanatory - number of threads
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636currently running and doing io, rate of io since last check, and the estimated
637completion percentage and time for the running group. It's impossible to
638estimate runtime of the following groups (if any).
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639
640When fio is done (or interrupted by ctrl-c), it will show the data for
641each thread, group of threads, and disks in that order. For each data
642direction, the output looks like:
643
644Client1 (g=0): err= 0:
645 write: io= 32MiB, bw= 666KiB/s, runt= 50320msec
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646 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
647 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
648 bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
71bfa161 649 cpu : usr=1.49%, sys=0.25%, ctx=7969
71619dc2 650 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
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651 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
652 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
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653
654The client number is printed, along with the group id and error of that
655thread. Below is the io statistics, here for writes. In the order listed,
656they denote:
657
658io= Number of megabytes io performed
659bw= Average bandwidth rate
660runt= The runtime of that thread
72fbda2a 661 slat= Submission latency (avg being the average, stdev being the
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662 standard deviation). This is the time it took to submit
663 the io. For sync io, the slat is really the completion
664 latency, since queue/complete is one operation there.
665 clat= Completion latency. Same names as slat, this denotes the
666 time from submission to completion of the io pieces. For
667 sync io, clat will usually be equal (or very close) to 0,
668 as the time from submit to complete is basically just
669 CPU time (io has already been done, see slat explanation).
670 bw= Bandwidth. Same names as the xlat stats, but also includes
671 an approximate percentage of total aggregate bandwidth
672 this thread received in this group. This last value is
673 only really useful if the threads in this group are on the
674 same disk, since they are then competing for disk access.
675cpu= CPU usage. User and system time, along with the number
676 of context switches this thread went through.
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677IO depths= The distribution of io depths over the job life time. The
678 numbers are divided into powers of 2, so for example the
679 16= entries includes depths up to that value but higher
680 than the previous entry. In other words, it covers the
681 range from 16 to 31.
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682IO latencies= The distribution of IO completion latencies. This is the
683 time from when IO leaves fio and when it gets completed.
684 The numbers follow the same pattern as the IO depths,
685 meaning that 2=1.6% means that 1.6% of the IO completed
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686 within 2 msecs, 20=12.8% means that 12.8% of the IO
687 took more than 10 msecs, but less than (or equal to) 20 msecs.
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688
689After each client has been listed, the group statistics are printed. They
690will look like this:
691
692Run status group 0 (all jobs):
693 READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
694 WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
695
696For each data direction, it prints:
697
698io= Number of megabytes io performed.
699aggrb= Aggregate bandwidth of threads in this group.
700minb= The minimum average bandwidth a thread saw.
701maxb= The maximum average bandwidth a thread saw.
702mint= The smallest runtime of the threads in that group.
703maxt= The longest runtime of the threads in that group.
704
705And finally, the disk statistics are printed. They will look like this:
706
707Disk stats (read/write):
708 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
709
710Each value is printed for both reads and writes, with reads first. The
711numbers denote:
712
713ios= Number of ios performed by all groups.
714merge= Number of merges io the io scheduler.
715ticks= Number of ticks we kept the disk busy.
716io_queue= Total time spent in the disk queue.
717util= The disk utilization. A value of 100% means we kept the disk
718 busy constantly, 50% would be a disk idling half of the time.
719
720
7217.0 Terse output
722----------------
723
724For scripted usage where you typically want to generate tables or graphs
6af019c9 725of the results, fio can output the results in a semicolon separated format.
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726The format is one long line of values, such as:
727
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728client1;0;0;1906777;1090804;1790;0;0;0.000000;0.000000;0;0;0.000000;0.000000;929380;1152890;25.510151%;1078276.333333;128948.113404;0;0;0;0;0;0.000000;0.000000;0;0;0.000000;0.000000;0;0;0.000000%;0.000000;0.000000;100.000000%;0.000000%;324;100.0%;0.0%;0.0%;0.0%;0.0%;0.0%;0.0%;100.0%;0.0%;0.0%;0.0%;0.0%;0.0%
729;0.0%;0.0%;0.0%;0.0%;0.0%
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730
731Split up, the format is as follows:
732
733 jobname, groupid, error
734 READ status:
735 KiB IO, bandwidth (KiB/sec), runtime (msec)
736 Submission latency: min, max, mean, deviation
737 Completion latency: min, max, mean, deviation
6c219763 738 Bw: min, max, aggregate percentage of total, mean, deviation
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739 WRITE status:
740 KiB IO, bandwidth (KiB/sec), runtime (msec)
741 Submission latency: min, max, mean, deviation
742 Completion latency: min, max, mean, deviation
6c219763 743 Bw: min, max, aggregate percentage of total, mean, deviation
71bfa161 744 CPU usage: user, system, context switches
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745 IO depths: <=1, 2, 4, 8, 16, 32, >=64
746 IO latencies: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000
747 Text description
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