Remove comment wrt sigaction() usage, it's deprecated
[fio.git] / HOWTO
CommitLineData
71bfa161
JA
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
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
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
b4692828
JA
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
c2b1e753
JA
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
71bfa161
JA
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.
71bfa161
JA
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
65db0851
JA
111section 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
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
c2b1e753
JA
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
71bfa161
JA
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
b4692828
JA
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
71bfa161
JA
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.
6d16ecb6
JA
173int Integer. A whole number value, can be negative. If prefixed with
174 0x, the integer is assumed to be of base 16 (hexidecimal).
71bfa161
JA
175siint SI integer. A whole number value, which may contain a postfix
176 describing the base of the number. Accepted postfixes are k/m/g,
6c219763 177 meaning kilo, mega, and giga. So if you want to specify 4096,
71bfa161
JA
178 you could either write out '4096' or just give 4k. The postfixes
179 signify base 2 values, so 1024 is 1k and 1024k is 1m and so on.
43159d18
JA
180 If the option accepts an upper and lower range, use a colon ':'
181 or minus '-' to seperate such values. See irange.
71bfa161
JA
182bool Boolean. Usually parsed as an integer, however only defined for
183 true and false (1 and 0).
184irange Integer range with postfix. Allows value range to be given, such
0c9baf91
JA
185 as 1024-4096. A colon may also be used as the seperator, eg
186 1k:4k. If the option allows two sets of ranges, they can be
187 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
188 siint.
71bfa161
JA
189
190With the above in mind, here follows the complete list of fio job
191parameters.
192
193name=str ASCII name of the job. This may be used to override the
194 name printed by fio for this job. Otherwise the job
c2b1e753 195 name is used. On the command line this parameter has the
6c219763 196 special purpose of also signaling the start of a new
c2b1e753 197 job.
71bfa161 198
61697c37
JA
199description=str Text description of the job. Doesn't do anything except
200 dump this text description when this job is run. It's
201 not parsed.
202
71bfa161
JA
203directory=str Prefix filenames with this directory. Used to places files
204 in a different location than "./".
205
206filename=str Fio normally makes up a filename based on the job name,
207 thread number, and file number. If you want to share
208 files between threads in a job or several jobs, specify
ed92ac0c
JA
209 a filename for each of them to override the default. If
210 the ioengine used is 'net', the filename is the host and
9f9214f2 211 port to connect to in the format of =host/port. If the
af52b345
JA
212 ioengine is file based, you can specify a number of files
213 by seperating the names with a ':' colon. So if you wanted
214 a job to open /dev/sda and /dev/sdb as the two working files,
66159828
JA
215 you would use filename=/dev/sda:/dev/sdb. '-' is a reserved
216 name, meaning stdin or stdout. Which of the two depends
217 on the read/write direction set.
71bfa161 218
bbf6b540
JA
219opendir=str Tell fio to recursively add any file it can find in this
220 directory and down the file system tree.
221
4d4e80f2
JA
222lockfile=str Fio defaults to not doing any locking files before it does
223 IO to them. If a file or file descriptor is shared, fio
224 can serialize IO to that file to make the end result
225 consistent. This is usual for emulating real workloads that
226 share files. The lock modes are:
227
228 none No locking. The default.
229 exclusive Only one thread/process may do IO,
230 excluding all others.
231 readwrite Read-write locking on the file. Many
232 readers may access the file at the
233 same time, but writes get exclusive
234 access.
235
236 The option may be post-fixed with a lock batch number. If
237 set, then each thread/process may do that amount of IOs to
238 the file before giving up the lock. Since lock acqusition is
239 expensive, batching the lock/unlocks will speed up IO.
29c1349f 240
d3aad8f2 241readwrite=str
71bfa161
JA
242rw=str Type of io pattern. Accepted values are:
243
244 read Sequential reads
245 write Sequential writes
246 randwrite Random writes
247 randread Random reads
248 rw Sequential mixed reads and writes
249 randrw Random mixed reads and writes
250
251 For the mixed io types, the default is to split them 50/50.
252 For certain types of io the result may still be skewed a bit,
211097b2
JA
253 since the speed may be different. It is possible to specify
254 a number of IO's to do before getting a new offset - this
255 is only useful for random IO, where fio would normally
256 generate a new random offset for every IO. If you append
257 eg 8 to randread, you would get a new random offset for
258 every 8 IO's. The result would be a seek for only every 8
259 IO's, instead of for every IO. Use rw=randread:8 to specify
260 that.
71bfa161 261
ee738499
JA
262randrepeat=bool For random IO workloads, seed the generator in a predictable
263 way so that results are repeatable across repetitions.
264
d2f3ac35
JA
265fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
266 on what IO patterns it is likely to issue. Sometimes you
267 want to test specific IO patterns without telling the
268 kernel about it, in which case you can disable this option.
269 If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
270 IO and POSIX_FADV_RANDOM for random IO.
271
7616cafe
JA
272size=siint The total size of file io for this job. Fio will run until
273 this many bytes has been transferred, unless runtime is
274 limited by other options (such as 'runtime', for instance).
275 Unless specific nr_files and filesize options are given,
276 fio will divide this size between the available files
277 specified by the job.
71bfa161 278
9c60ce64
JA
279filesize=siint Individual file sizes. May be a range, in which case fio
280 will select sizes for files at random within the given range
281 and limited to 'size' in total (if that is given). If not
282 given, each created file is the same size.
283
aa31f1f1
SL
284fill_device=bool Sets size to something really large and waits for ENOSPC (no
285 space left on device) as the terminating condition. Only makes
286 sense with sequential write.
287
d3aad8f2 288blocksize=siint
f90eff5a
JA
289bs=siint The block size used for the io units. Defaults to 4k. Values
290 can be given for both read and writes. If a single siint is
291 given, it will apply to both. If a second siint is specified
292 after a comma, it will apply to writes only. In other words,
293 the format is either bs=read_and_write or bs=read,write.
294 bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
787f7e95
JA
295 for writes. If you only wish to set the write size, you
296 can do so by passing an empty read size - bs=,8k will set
297 8k for writes and leave the read default value.
a00735e6 298
d3aad8f2 299blocksize_range=irange
71bfa161
JA
300bsrange=irange Instead of giving a single block size, specify a range
301 and fio will mix the issued io block sizes. The issued
302 io unit will always be a multiple of the minimum value
f90eff5a
JA
303 given (also see bs_unaligned). Applies to both reads and
304 writes, however a second range can be given after a comma.
305 See bs=.
a00735e6 306
564ca972
JA
307bssplit=str Sometimes you want even finer grained control of the
308 block sizes issued, not just an even split between them.
309 This option allows you to weight various block sizes,
310 so that you are able to define a specific amount of
311 block sizes issued. The format for this option is:
312
313 bssplit=blocksize/percentage:blocksize/percentage
314
315 for as many block sizes as needed. So if you want to define
316 a workload that has 50% 64k blocks, 10% 4k blocks, and
317 40% 32k blocks, you would write:
318
319 bssplit=4k/10:64k/50:32k/40
320
321 Ordering does not matter. If the percentage is left blank,
322 fio will fill in the remaining values evenly. So a bssplit
323 option like this one:
324
325 bssplit=4k/50:1k/:32k/
326
327 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
328 always add up to 100, if bssplit is given a range that adds
329 up to more, it will error out.
330
d3aad8f2 331blocksize_unaligned
690adba3
JA
332bs_unaligned If this option is given, any byte size value within bsrange
333 may be used as a block range. This typically wont work with
334 direct IO, as that normally requires sector alignment.
71bfa161 335
e9459e5a
JA
336zero_buffers If this option is given, fio will init the IO buffers to
337 all zeroes. The default is to fill them with random data.
338
5973cafb
JA
339refill_buffers If this option is given, fio will refill the IO buffers
340 on every submit. The default is to only fill it at init
341 time and reuse that data. Only makes sense if zero_buffers
41ccd845
JA
342 isn't specified, naturally. If data verification is enabled,
343 refill_buffers is also automatically enabled.
5973cafb 344
71bfa161
JA
345nrfiles=int Number of files to use for this job. Defaults to 1.
346
390b1537
JA
347openfiles=int Number of files to keep open at the same time. Defaults to
348 the same as nrfiles, can be set smaller to limit the number
349 simultaneous opens.
350
5af1c6f3
JA
351file_service_type=str Defines how fio decides which file from a job to
352 service next. The following types are defined:
353
354 random Just choose a file at random.
355
356 roundrobin Round robin over open files. This
357 is the default.
358
1907dbc6
JA
359 The string can have a number appended, indicating how
360 often to switch to a new file. So if option random:4 is
361 given, fio will switch to a new random file after 4 ios
362 have been issued.
363
71bfa161
JA
364ioengine=str Defines how the job issues io to the file. The following
365 types are defined:
366
367 sync Basic read(2) or write(2) io. lseek(2) is
368 used to position the io location.
369
a31041ea 370 psync Basic pread(2) or pwrite(2) io.
371
e05af9e5 372 vsync Basic readv(2) or writev(2) IO.
1d2af02a 373
71bfa161
JA
374 libaio Linux native asynchronous io.
375
376 posixaio glibc posix asynchronous io.
377
417f0068
JA
378 solarisaio Solaris native asynchronous io.
379
71bfa161
JA
380 mmap File is memory mapped and data copied
381 to/from using memcpy(3).
382
383 splice splice(2) is used to transfer the data and
384 vmsplice(2) to transfer data from user
385 space to the kernel.
386
d0ff85df
JA
387 syslet-rw Use the syslet system calls to make
388 regular read/write async.
389
71bfa161 390 sg SCSI generic sg v3 io. May either be
6c219763 391 synchronous using the SG_IO ioctl, or if
71bfa161
JA
392 the target is an sg character device
393 we use read(2) and write(2) for asynchronous
394 io.
395
a94ea28b
JA
396 null Doesn't transfer any data, just pretends
397 to. This is mainly used to exercise fio
398 itself and for debugging/testing purposes.
399
ed92ac0c
JA
400 net Transfer over the network to given host:port.
401 'filename' must be set appropriately to
9f9214f2 402 filename=host/port regardless of send
ed92ac0c
JA
403 or receive, if the latter only the port
404 argument is used.
405
9cce02e8
JA
406 netsplice Like net, but uses splice/vmsplice to
407 map data and send/receive.
408
53aec0a4 409 cpuio Doesn't transfer any data, but burns CPU
ba0fbe10
JA
410 cycles according to the cpuload= and
411 cpucycle= options. Setting cpuload=85
412 will cause that job to do nothing but burn
36ecec83
GP
413 85% of the CPU. In case of SMP machines,
414 use numjobs=<no_of_cpu> to get desired CPU
415 usage, as the cpuload only loads a single
416 CPU at the desired rate.
ba0fbe10 417
e9a1806f
JA
418 guasi The GUASI IO engine is the Generic Userspace
419 Asyncronous Syscall Interface approach
420 to async IO. See
421
422 http://www.xmailserver.org/guasi-lib.html
423
424 for more info on GUASI.
425
8a7bd877
JA
426 external Prefix to specify loading an external
427 IO engine object file. Append the engine
428 filename, eg ioengine=external:/tmp/foo.o
429 to load ioengine foo.o in /tmp.
430
71bfa161
JA
431iodepth=int This defines how many io units to keep in flight against
432 the file. The default is 1 for each file defined in this
433 job, can be overridden with a larger value for higher
434 concurrency.
435
cb5ab512 436iodepth_batch=int This defines how many pieces of IO to submit at once.
89e820f6
JA
437 It defaults to 1 which means that we submit each IO
438 as soon as it is available, but can be raised to submit
439 bigger batches of IO at the time.
cb5ab512 440
e916b390
JA
441iodepth_low=int The low water mark indicating when to start filling
442 the queue again. Defaults to the same as iodepth, meaning
443 that fio will attempt to keep the queue full at all times.
444 If iodepth is set to eg 16 and iodepth_low is set to 4, then
445 after fio has filled the queue of 16 requests, it will let
446 the depth drain down to 4 before starting to fill it again.
447
71bfa161 448direct=bool If value is true, use non-buffered io. This is usually
76a43db4
JA
449 O_DIRECT.
450
451buffered=bool If value is true, use buffered io. This is the opposite
452 of the 'direct' option. Defaults to true.
71bfa161
JA
453
454offset=siint Start io at the given offset in the file. The data before
455 the given offset will not be touched. This effectively
456 caps the file size at real_size - offset.
457
458fsync=int If writing to a file, issue a sync of the dirty data
459 for every number of blocks given. For example, if you give
460 32 as a parameter, fio will sync the file for every 32
461 writes issued. If fio is using non-buffered io, we may
462 not sync the file. The exception is the sg io engine, which
6c219763 463 synchronizes the disk cache anyway.
71bfa161 464
5036fc1e
JA
465overwrite=bool If true, writes to a file will always overwrite existing
466 data. If the file doesn't already exist, it will be
467 created before the write phase begins. If the file exists
468 and is large enough for the specified write phase, nothing
469 will be done.
71bfa161
JA
470
471end_fsync=bool If true, fsync file contents when the job exits.
472
ebb1415f
JA
473fsync_on_close=bool If true, fio will fsync() a dirty file on close.
474 This differs from end_fsync in that it will happen on every
475 file close, not just at the end of the job.
476
71bfa161
JA
477rwmixread=int How large a percentage of the mix should be reads.
478
479rwmixwrite=int How large a percentage of the mix should be writes. If both
480 rwmixread and rwmixwrite is given and the values do not add
481 up to 100%, the latter of the two will be used to override
482 the first.
483
bb8895e0
JA
484norandommap Normally fio will cover every block of the file when doing
485 random IO. If this option is given, fio will just get a
486 new random offset without looking at past io history. This
487 means that some blocks may not be read or written, and that
488 some blocks may be read/written more than once. This option
7616cafe
JA
489 is mutually exclusive with verify= for that reason, since
490 fio doesn't track potential block rewrites which may alter
491 the calculated checksum for that block.
bb8895e0 492
2b386d25
JA
493softrandommap See norandommap. If fio runs with the random block map enabled
494 and it fails to allocate the map, if this option is set it
495 will continue without a random block map. As coverage will
496 not be as complete as with random maps, this option is
497 disabled by default.
498
71bfa161
JA
499nice=int Run the job with the given nice value. See man nice(2).
500
501prio=int Set the io priority value of this job. Linux limits us to
502 a positive value between 0 and 7, with 0 being the highest.
503 See man ionice(1).
504
505prioclass=int Set the io priority class. See man ionice(1).
506
507thinktime=int Stall the job x microseconds after an io has completed before
508 issuing the next. May be used to simulate processing being
48097d5c
JA
509 done by an application. See thinktime_blocks and
510 thinktime_spin.
511
512thinktime_spin=int
513 Only valid if thinktime is set - pretend to spend CPU time
514 doing something with the data received, before falling back
515 to sleeping for the rest of the period specified by
516 thinktime.
9c1f7434
JA
517
518thinktime_blocks
519 Only valid if thinktime is set - control how many blocks
520 to issue, before waiting 'thinktime' usecs. If not set,
521 defaults to 1 which will make fio wait 'thinktime' usecs
522 after every block.
71bfa161
JA
523
524rate=int Cap the bandwidth used by this job to this number of KiB/sec.
525
526ratemin=int Tell fio to do whatever it can to maintain at least this
4e991c23
JA
527 bandwidth. Failing to meet this requirement, will cause
528 the job to exit.
529
530rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
531 as rate, just specified independently of bandwidth. If the
532 job is given a block size range instead of a fixed value,
533 the smallest block size is used as the metric.
534
535rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
536 the job to exit.
71bfa161
JA
537
538ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number
6c219763 539 of milliseconds.
71bfa161
JA
540
541cpumask=int Set the CPU affinity of this job. The parameter given is a
a08bc17f
JA
542 bitmask of allowed CPU's the job may run on. So if you want
543 the allowed CPUs to be 1 and 5, you would pass the decimal
544 value of (1 << 1 | 1 << 5), or 34. See man
7dbb6eba
JA
545 sched_setaffinity(2). This may not work on all supported
546 operating systems or kernel versions.
71bfa161 547
d2e268b0
JA
548cpus_allowed=str Controls the same options as cpumask, but it allows a text
549 setting of the permitted CPUs instead. So to use CPUs 1 and
550 5, you would specify cpus_allowed=1,5.
551
71bfa161
JA
552startdelay=int Start this job the specified number of seconds after fio
553 has started. Only useful if the job file contains several
554 jobs, and you want to delay starting some jobs to a certain
555 time.
556
03b74b3e 557runtime=int Tell fio to terminate processing after the specified number
71bfa161
JA
558 of seconds. It can be quite hard to determine for how long
559 a specified job will run, so this parameter is handy to
560 cap the total runtime to a given time.
561
cf4464ca
JA
562time_based If set, fio will run for the duration of the runtime
563 specified even if the file(s) are completey read or
564 written. It will simply loop over the same workload
565 as many times as the runtime allows.
566
71bfa161
JA
567invalidate=bool Invalidate the buffer/page cache parts for this file prior
568 to starting io. Defaults to true.
569
570sync=bool Use sync io for buffered writes. For the majority of the
571 io engines, this means using O_SYNC.
572
d3aad8f2 573iomem=str
71bfa161
JA
574mem=str Fio can use various types of memory as the io unit buffer.
575 The allowed values are:
576
577 malloc Use memory from malloc(3) as the buffers.
578
579 shm Use shared memory as the buffers. Allocated
580 through shmget(2).
581
74b025b0
JA
582 shmhuge Same as shm, but use huge pages as backing.
583
313cb206
JA
584 mmap Use mmap to allocate buffers. May either be
585 anonymous memory, or can be file backed if
586 a filename is given after the option. The
587 format is mem=mmap:/path/to/file.
71bfa161 588
d0bdaf49
JA
589 mmaphuge Use a memory mapped huge file as the buffer
590 backing. Append filename after mmaphuge, ala
591 mem=mmaphuge:/hugetlbfs/file
592
71bfa161 593 The area allocated is a function of the maximum allowed
5394ae5f
JA
594 bs size for the job, multiplied by the io depth given. Note
595 that for shmhuge and mmaphuge to work, the system must have
596 free huge pages allocated. This can normally be checked
597 and set by reading/writing /proc/sys/vm/nr_hugepages on a
598 Linux system. Fio assumes a huge page is 4MiB in size. So
599 to calculate the number of huge pages you need for a given
600 job file, add up the io depth of all jobs (normally one unless
601 iodepth= is used) and multiply by the maximum bs set. Then
602 divide that number by the huge page size. You can see the
603 size of the huge pages in /proc/meminfo. If no huge pages
604 are allocated by having a non-zero number in nr_hugepages,
56bb17f2 605 using mmaphuge or shmhuge will fail. Also see hugepage-size.
5394ae5f
JA
606
607 mmaphuge also needs to have hugetlbfs mounted and the file
608 location should point there. So if it's mounted in /huge,
609 you would use mem=mmaphuge:/huge/somefile.
71bfa161 610
56bb17f2
JA
611hugepage-size=siint
612 Defines the size of a huge page. Must at least be equal
613 to the system setting, see /proc/meminfo. Defaults to 4MiB.
c51074e7
JA
614 Should probably always be a multiple of megabytes, so using
615 hugepage-size=Xm is the preferred way to set this to avoid
616 setting a non-pow-2 bad value.
56bb17f2 617
71bfa161
JA
618exitall When one job finishes, terminate the rest. The default is
619 to wait for each job to finish, sometimes that is not the
620 desired action.
621
622bwavgtime=int Average the calculated bandwidth over the given time. Value
6c219763 623 is specified in milliseconds.
71bfa161
JA
624
625create_serialize=bool If true, serialize the file creating for the jobs.
626 This may be handy to avoid interleaving of data
627 files, which may greatly depend on the filesystem
628 used and even the number of processors in the system.
629
630create_fsync=bool fsync the data file after creation. This is the
631 default.
632
e545a6ce
JA
633unlink=bool Unlink the job files when done. Not the default, as repeated
634 runs of that job would then waste time recreating the fileset
635 again and again.
71bfa161
JA
636
637loops=int Run the specified number of iterations of this job. Used
638 to repeat the same workload a given number of times. Defaults
639 to 1.
640
68e1f29a 641do_verify=bool Run the verify phase after a write phase. Only makes sense if
e84c73a8
SL
642 verify is set. Defaults to 1.
643
71bfa161
JA
644verify=str If writing to a file, fio can verify the file contents
645 after each iteration of the job. The allowed values are:
646
647 md5 Use an md5 sum of the data area and store
648 it in the header of each block.
649
17dc34df
JA
650 crc64 Use an experimental crc64 sum of the data
651 area and store it in the header of each
652 block.
653
71bfa161
JA
654 crc32 Use a crc32 sum of the data area and store
655 it in the header of each block.
656
969f7ed3
JA
657 crc16 Use a crc16 sum of the data area and store
658 it in the header of each block.
659
17dc34df
JA
660 crc7 Use a crc7 sum of the data area and store
661 it in the header of each block.
662
cd14cc10
JA
663 sha512 Use sha512 as the checksum function.
664
665 sha256 Use sha256 as the checksum function.
666
7437ee87
SL
667 meta Write extra information about each io
668 (timestamp, block number etc.). The block
669 number is verified.
670
36690c9b
JA
671 null Only pretend to verify. Useful for testing
672 internals with ioengine=null, not for much
673 else.
674
6c219763 675 This option can be used for repeated burn-in tests of a
71bfa161
JA
676 system to make sure that the written data is also
677 correctly read back.
678
160b966d
JA
679verifysort=bool If set, fio will sort written verify blocks when it deems
680 it faster to read them back in a sorted manner. This is
681 often the case when overwriting an existing file, since
682 the blocks are already laid out in the file system. You
683 can ignore this option unless doing huge amounts of really
684 fast IO where the red-black tree sorting CPU time becomes
685 significant.
3f9f4e26 686
a59e170d 687verify_offset=siint Swap the verification header with data somewhere else
546a9142
SL
688 in the block before writing. Its swapped back before
689 verifying.
690
a59e170d 691verify_interval=siint Write the verification header at a finer granularity
3f9f4e26
SL
692 than the blocksize. It will be written for chunks the
693 size of header_interval. blocksize should divide this
694 evenly.
90059d65 695
e28218f3
SL
696verify_pattern=int If set, fio will fill the io buffers with this
697 pattern. Fio defaults to filling with totally random
698 bytes, but sometimes it's interesting to fill with a known
699 pattern for io verification purposes. Depending on the
700 width of the pattern, fio will fill 1/2/3/4 bytes of the
701 buffer at the time. The verify_pattern cannot be larger than
702 a 32-bit quantity.
703
68e1f29a 704verify_fatal=bool Normally fio will keep checking the entire contents
a12a3b4d
JA
705 before quitting on a block verification failure. If this
706 option is set, fio will exit the job on the first observed
707 failure.
160b966d 708
71bfa161
JA
709stonewall Wait for preceeding jobs in the job file to exit, before
710 starting this one. Can be used to insert serialization
b3d62a75
JA
711 points in the job file. A stone wall also implies starting
712 a new reporting group.
713
714new_group Start a new reporting group. If this option isn't given,
715 jobs in a file will be part of the same reporting group
716 unless seperated by a stone wall (or if it's a group
717 by itself, with the numjobs option).
71bfa161
JA
718
719numjobs=int Create the specified number of clones of this job. May be
720 used to setup a larger number of threads/processes doing
fa28c85a
JA
721 the same thing. We regard that grouping of jobs as a
722 specific group.
723
724group_reporting If 'numjobs' is set, it may be interesting to display
725 statistics for the group as a whole instead of for each
726 individual job. This is especially true of 'numjobs' is
727 large, looking at individual thread/process output quickly
728 becomes unwieldy. If 'group_reporting' is specified, fio
729 will show the final report per-group instead of per-job.
71bfa161
JA
730
731thread fio defaults to forking jobs, however if this option is
732 given, fio will use pthread_create(3) to create threads
733 instead.
734
735zonesize=siint Divide a file into zones of the specified size. See zoneskip.
736
737zoneskip=siint Skip the specified number of bytes when zonesize data has
738 been read. The two zone options can be used to only do
739 io on zones of a file.
740
076efc7c
JA
741write_iolog=str Write the issued io patterns to the specified file. See
742 read_iolog.
71bfa161 743
076efc7c 744read_iolog=str Open an iolog with the specified file name and replay the
71bfa161 745 io patterns it contains. This can be used to store a
6df8adaa
JA
746 workload and replay it sometime later. The iolog given
747 may also be a blktrace binary file, which allows fio
748 to replay a workload captured by blktrace. See blktrace
749 for how to capture such logging data. For blktrace replay,
750 the file needs to be turned into a blkparse binary data
751 file first (blktrace <device> -d file_for_fio.bin).
71bfa161
JA
752
753write_bw_log If given, write a bandwidth log of the jobs in this job
754 file. Can be used to store data of the bandwidth of the
e0da9bc2
JA
755 jobs in their lifetime. The included fio_generate_plots
756 script uses gnuplot to turn these text files into nice
757 graphs.
71bfa161
JA
758
759write_lat_log Same as write_bw_log, except that this option stores io
760 completion latencies instead.
761
762lockmem=siint Pin down the specified amount of memory with mlock(2). Can
763 potentially be used instead of removing memory or booting
764 with less memory to simulate a smaller amount of memory.
765
766exec_prerun=str Before running this job, issue the command specified
767 through system(3).
768
769exec_postrun=str After the job completes, issue the command specified
770 though system(3).
771
772ioscheduler=str Attempt to switch the device hosting the file to the specified
773 io scheduler before running.
774
775cpuload=int If the job is a CPU cycle eater, attempt to use the specified
776 percentage of CPU cycles.
777
778cpuchunks=int If the job is a CPU cycle eater, split the load into
6c219763 779 cycles of the given time. In milliseconds.
71bfa161 780
0a839f30
JA
781disk_util=bool Generate disk utilization statistics, if the platform
782 supports it. Defaults to on.
783
71bfa161
JA
784
7856.0 Interpreting the output
786---------------------------
787
788fio spits out a lot of output. While running, fio will display the
789status of the jobs created. An example of that would be:
790
73c8b082 791Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
71bfa161
JA
792
793The characters inside the square brackets denote the current status of
794each thread. The possible values (in typical life cycle order) are:
795
796Idle Run
797---- ---
798P Thread setup, but not started.
799C Thread created.
800I Thread initialized, waiting.
801 R Running, doing sequential reads.
802 r Running, doing random reads.
803 W Running, doing sequential writes.
804 w Running, doing random writes.
805 M Running, doing mixed sequential reads/writes.
806 m Running, doing mixed random reads/writes.
807 F Running, currently waiting for fsync()
808V Running, doing verification of written data.
809E Thread exited, not reaped by main thread yet.
810_ Thread reaped.
811
812The other values are fairly self explanatory - number of threads
c9f60304
JA
813currently running and doing io, rate of io since last check (read speed
814listed first, then write speed), and the estimated completion percentage
815and time for the running group. It's impossible to estimate runtime of
816the following groups (if any).
71bfa161
JA
817
818When fio is done (or interrupted by ctrl-c), it will show the data for
819each thread, group of threads, and disks in that order. For each data
820direction, the output looks like:
821
822Client1 (g=0): err= 0:
823 write: io= 32MiB, bw= 666KiB/s, runt= 50320msec
6104ddb6
JA
824 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
825 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
826 bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
e7823a94 827 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
71619dc2 828 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
829 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
830 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
30061b97 831 issued r/w: total=0/32768, short=0/0
8abdce66
JA
832 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
833 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
71bfa161
JA
834
835The client number is printed, along with the group id and error of that
836thread. Below is the io statistics, here for writes. In the order listed,
837they denote:
838
839io= Number of megabytes io performed
840bw= Average bandwidth rate
841runt= The runtime of that thread
72fbda2a 842 slat= Submission latency (avg being the average, stdev being the
71bfa161
JA
843 standard deviation). This is the time it took to submit
844 the io. For sync io, the slat is really the completion
8a35c71e
JA
845 latency, since queue/complete is one operation there. This
846 value can be in miliseconds or microseconds, fio will choose
847 the most appropriate base and print that. In the example
848 above, miliseconds is the best scale.
71bfa161
JA
849 clat= Completion latency. Same names as slat, this denotes the
850 time from submission to completion of the io pieces. For
851 sync io, clat will usually be equal (or very close) to 0,
852 as the time from submit to complete is basically just
853 CPU time (io has already been done, see slat explanation).
854 bw= Bandwidth. Same names as the xlat stats, but also includes
855 an approximate percentage of total aggregate bandwidth
856 this thread received in this group. This last value is
857 only really useful if the threads in this group are on the
858 same disk, since they are then competing for disk access.
859cpu= CPU usage. User and system time, along with the number
e7823a94
JA
860 of context switches this thread went through, usage of
861 system and user time, and finally the number of major
862 and minor page faults.
71619dc2
JA
863IO depths= The distribution of io depths over the job life time. The
864 numbers are divided into powers of 2, so for example the
865 16= entries includes depths up to that value but higher
866 than the previous entry. In other words, it covers the
867 range from 16 to 31.
838bc709
JA
868IO submit= How many pieces of IO were submitting in a single submit
869 call. Each entry denotes that amount and below, until
870 the previous entry - eg, 8=100% mean that we submitted
871 anywhere in between 5-8 ios per submit call.
872IO complete= Like the above submit number, but for completions instead.
30061b97
JA
873IO issued= The number of read/write requests issued, and how many
874 of them were short.
ec118304
JA
875IO latencies= The distribution of IO completion latencies. This is the
876 time from when IO leaves fio and when it gets completed.
877 The numbers follow the same pattern as the IO depths,
878 meaning that 2=1.6% means that 1.6% of the IO completed
8abdce66
JA
879 within 2 msecs, 20=12.8% means that 12.8% of the IO
880 took more than 10 msecs, but less than (or equal to) 20 msecs.
71bfa161
JA
881
882After each client has been listed, the group statistics are printed. They
883will look like this:
884
885Run status group 0 (all jobs):
886 READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
887 WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
888
889For each data direction, it prints:
890
891io= Number of megabytes io performed.
892aggrb= Aggregate bandwidth of threads in this group.
893minb= The minimum average bandwidth a thread saw.
894maxb= The maximum average bandwidth a thread saw.
895mint= The smallest runtime of the threads in that group.
896maxt= The longest runtime of the threads in that group.
897
898And finally, the disk statistics are printed. They will look like this:
899
900Disk stats (read/write):
901 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
902
903Each value is printed for both reads and writes, with reads first. The
904numbers denote:
905
906ios= Number of ios performed by all groups.
907merge= Number of merges io the io scheduler.
908ticks= Number of ticks we kept the disk busy.
909io_queue= Total time spent in the disk queue.
910util= The disk utilization. A value of 100% means we kept the disk
911 busy constantly, 50% would be a disk idling half of the time.
912
913
9147.0 Terse output
915----------------
916
917For scripted usage where you typically want to generate tables or graphs
6af019c9 918of the results, fio can output the results in a semicolon separated format.
71bfa161
JA
919The format is one long line of values, such as:
920
6af019c9
JA
921client1;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%
922;0.0%;0.0%;0.0%;0.0%;0.0%
71bfa161
JA
923
924Split up, the format is as follows:
925
926 jobname, groupid, error
927 READ status:
928 KiB IO, bandwidth (KiB/sec), runtime (msec)
929 Submission latency: min, max, mean, deviation
930 Completion latency: min, max, mean, deviation
6c219763 931 Bw: min, max, aggregate percentage of total, mean, deviation
71bfa161
JA
932 WRITE status:
933 KiB IO, bandwidth (KiB/sec), runtime (msec)
934 Submission latency: min, max, mean, deviation
935 Completion latency: min, max, mean, deviation
6c219763 936 Bw: min, max, aggregate percentage of total, mean, deviation
046ee302 937 CPU usage: user, system, context switches, major faults, minor faults
2270890c
JA
938 IO depths: <=1, 2, 4, 8, 16, 32, >=64
939 IO latencies: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000
940 Text description
71bfa161 941