8 5. Detailed list of parameters
12 9. CPU idleness profiling
14 1.0 Overview and history
15 ------------------------
16 fio was originally written to save me the hassle of writing special test
17 case programs when I wanted to test a specific workload, either for
18 performance reasons or to find/reproduce a bug. The process of writing
19 such a test app can be tiresome, especially if you have to do it often.
20 Hence I needed a tool that would be able to simulate a given io workload
21 without resorting to writing a tailored test case again and again.
23 A test work load is difficult to define, though. There can be any number
24 of processes or threads involved, and they can each be using their own
25 way of generating io. You could have someone dirtying large amounts of
26 memory in an memory mapped file, or maybe several threads issuing
27 reads using asynchronous io. fio needed to be flexible enough to
28 simulate both of these cases, and many more.
32 The first step in getting fio to simulate a desired io workload, is
33 writing a job file describing that specific setup. A job file may contain
34 any number of threads and/or files - the typical contents of the job file
35 is a global section defining shared parameters, and one or more job
36 sections describing the jobs involved. When run, fio parses this file
37 and sets everything up as described. If we break down a job from top to
38 bottom, it contains the following basic parameters:
40 IO type Defines the io pattern issued to the file(s).
41 We may only be reading sequentially from this
42 file(s), or we may be writing randomly. Or even
43 mixing reads and writes, sequentially or randomly.
45 Block size In how large chunks are we issuing io? This may be
46 a single value, or it may describe a range of
49 IO size How much data are we going to be reading/writing.
51 IO engine How do we issue io? We could be memory mapping the
52 file, we could be using regular read/write, we
53 could be using splice, async io, syslet, or even
56 IO depth If the io engine is async, how large a queuing
57 depth do we want to maintain?
59 IO type Should we be doing buffered io, or direct/raw io?
61 Num files How many files are we spreading the workload over.
63 Num threads How many threads or processes should we spread
66 The above are the basic parameters defined for a workload, in addition
67 there's a multitude of parameters that modify other aspects of how this
73 See the README file for command line parameters, there are only a few
76 Running fio is normally the easiest part - you just give it the job file
77 (or job files) as parameters:
81 and it will start doing what the job_file tells it to do. You can give
82 more than one job file on the command line, fio will serialize the running
83 of those files. Internally that is the same as using the 'stonewall'
84 parameter described the the parameter section.
86 If the job file contains only one job, you may as well just give the
87 parameters on the command line. The command line parameters are identical
88 to the job parameters, with a few extra that control global parameters
89 (see README). For example, for the job file parameter iodepth=2, the
90 mirror command line option would be --iodepth 2 or --iodepth=2. You can
91 also use the command line for giving more than one job entry. For each
92 --name option that fio sees, it will start a new job with that name.
93 Command line entries following a --name entry will apply to that job,
94 until there are no more entries or a new --name entry is seen. This is
95 similar to the job file options, where each option applies to the current
96 job until a new [] job entry is seen.
98 fio does not need to run as root, except if the files or devices specified
99 in the job section requires that. Some other options may also be restricted,
100 such as memory locking, io scheduler switching, and decreasing the nice value.
105 As previously described, fio accepts one or more job files describing
106 what it is supposed to do. The job file format is the classic ini file,
107 where the names enclosed in [] brackets define the job name. You are free
108 to use any ascii name you want, except 'global' which has special meaning.
109 A global section sets defaults for the jobs described in that file. A job
110 may override a global section parameter, and a job file may even have
111 several global sections if so desired. A job is only affected by a global
112 section residing above it. If the first character in a line is a ';' or a
113 '#', the entire line is discarded as a comment.
115 So let's look at a really simple job file that defines two processes, each
116 randomly reading from a 128MB file.
118 ; -- start job file --
129 As you can see, the job file sections themselves are empty as all the
130 described parameters are shared. As no filename= option is given, fio
131 makes up a filename for each of the jobs as it sees fit. On the command
132 line, this job would look as follows:
134 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
137 Let's look at an example that has a number of processes writing randomly
140 ; -- start job file --
152 Here we have no global section, as we only have one job defined anyway.
153 We want to use async io here, with a depth of 4 for each file. We also
154 increased the buffer size used to 32KB and define numjobs to 4 to
155 fork 4 identical jobs. The result is 4 processes each randomly writing
156 to their own 64MB file. Instead of using the above job file, you could
157 have given the parameters on the command line. For this case, you would
160 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
162 4.1 Environment variables
163 -------------------------
165 fio also supports environment variable expansion in job files. Any
166 substring of the form "${VARNAME}" as part of an option value (in other
167 words, on the right of the `='), will be expanded to the value of the
168 environment variable called VARNAME. If no such environment variable
169 is defined, or VARNAME is the empty string, the empty string will be
172 As an example, let's look at a sample fio invocation and job file:
174 $ SIZE=64m NUMJOBS=4 fio jobfile.fio
176 ; -- start job file --
183 This will expand to the following equivalent job file at runtime:
185 ; -- start job file --
192 fio ships with a few example job files, you can also look there for
195 4.2 Reserved keywords
196 ---------------------
198 Additionally, fio has a set of reserved keywords that will be replaced
199 internally with the appropriate value. Those keywords are:
201 $pagesize The architecture page size of the running system
202 $mb_memory Megabytes of total memory in the system
203 $ncpus Number of online available CPUs
205 These can be used on the command line or in the job file, and will be
206 automatically substituted with the current system values when the job
207 is run. Simple math is also supported on these keywords, so you can
208 perform actions like:
212 and get that properly expanded to 8 times the size of memory in the
216 5.0 Detailed list of parameters
217 -------------------------------
219 This section describes in details each parameter associated with a job.
220 Some parameters take an option of a given type, such as an integer or
221 a string. The following types are used:
223 str String. This is a sequence of alpha characters.
224 time Integer with possible time suffix. In seconds unless otherwise
225 specified, use eg 10m for 10 minutes. Accepts s/m/h for seconds,
227 int SI integer. A whole number value, which may contain a suffix
228 describing the base of the number. Accepted suffixes are k/m/g/t/p,
229 meaning kilo, mega, giga, tera, and peta. The suffix is not case
230 sensitive, and you may also include trailing 'b' (eg 'kb' is the same
231 as 'k'). So if you want to specify 4096, you could either write
232 out '4096' or just give 4k. The suffixes signify base 2 values, so
233 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly
234 set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the
235 case, then 1000 is used as the multiplier. This can be handy for
236 disks, since manufacturers generally use base 10 values when listing
237 the capacity of a drive. If the option accepts an upper and lower
238 range, use a colon ':' or minus '-' to separate such values. May also
239 include a prefix to indicate numbers base. If 0x is used, the number
240 is assumed to be hexadecimal. See irange.
241 bool Boolean. Usually parsed as an integer, however only defined for
242 true and false (1 and 0).
243 irange Integer range with suffix. Allows value range to be given, such
244 as 1024-4096. A colon may also be used as the separator, eg
245 1k:4k. If the option allows two sets of ranges, they can be
246 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
248 float_list A list of floating numbers, separated by a ':' character.
250 With the above in mind, here follows the complete list of fio job
253 name=str ASCII name of the job. This may be used to override the
254 name printed by fio for this job. Otherwise the job
255 name is used. On the command line this parameter has the
256 special purpose of also signaling the start of a new
259 description=str Text description of the job. Doesn't do anything except
260 dump this text description when this job is run. It's
263 directory=str Prefix filenames with this directory. Used to place files
264 in a different location than "./".
266 filename=str Fio normally makes up a filename based on the job name,
267 thread number, and file number. If you want to share
268 files between threads in a job or several jobs, specify
269 a filename for each of them to override the default. If
270 the ioengine used is 'net', the filename is the host, port,
271 and protocol to use in the format of =host,port,protocol.
272 See ioengine=net for more. If the ioengine is file based, you
273 can specify a number of files by separating the names with a
274 ':' colon. So if you wanted a job to open /dev/sda and /dev/sdb
275 as the two working files, you would use
276 filename=/dev/sda:/dev/sdb. On Windows, disk devices are
277 accessed as \\.\PhysicalDrive0 for the first device,
278 \\.\PhysicalDrive1 for the second etc. Note: Windows and
279 FreeBSD prevent write access to areas of the disk containing
280 in-use data (e.g. filesystems).
281 If the wanted filename does need to include a colon, then
282 escape that with a '\' character. For instance, if the filename
283 is "/dev/dsk/foo@3,0:c", then you would use
284 filename="/dev/dsk/foo@3,0\:c". '-' is a reserved name, meaning
285 stdin or stdout. Which of the two depends on the read/write
289 If sharing multiple files between jobs, it is usually necessary
290 to have fio generate the exact names that you want. By default,
291 fio will name a file based on the default file format
292 specification of jobname.jobnumber.filenumber. With this
293 option, that can be customized. Fio will recognize and replace
294 the following keywords in this string:
297 The name of the worker thread or process.
300 The incremental number of the worker thread or
304 The incremental number of the file for that worker
307 To have dependent jobs share a set of files, this option can
308 be set to have fio generate filenames that are shared between
309 the two. For instance, if testfiles.$filenum is specified,
310 file number 4 for any job will be named testfiles.4. The
311 default of $jobname.$jobnum.$filenum will be used if
312 no other format specifier is given.
314 opendir=str Tell fio to recursively add any file it can find in this
315 directory and down the file system tree.
317 lockfile=str Fio defaults to not locking any files before it does
318 IO to them. If a file or file descriptor is shared, fio
319 can serialize IO to that file to make the end result
320 consistent. This is usual for emulating real workloads that
321 share files. The lock modes are:
323 none No locking. The default.
324 exclusive Only one thread/process may do IO,
325 excluding all others.
326 readwrite Read-write locking on the file. Many
327 readers may access the file at the
328 same time, but writes get exclusive
332 rw=str Type of io pattern. Accepted values are:
334 read Sequential reads
335 write Sequential writes
336 randwrite Random writes
337 randread Random reads
338 rw,readwrite Sequential mixed reads and writes
339 randrw Random mixed reads and writes
341 For the mixed io types, the default is to split them 50/50.
342 For certain types of io the result may still be skewed a bit,
343 since the speed may be different. It is possible to specify
344 a number of IO's to do before getting a new offset, this is
345 one by appending a ':<nr>' to the end of the string given.
346 For a random read, it would look like 'rw=randread:8' for
347 passing in an offset modifier with a value of 8. If the
348 suffix is used with a sequential IO pattern, then the value
349 specified will be added to the generated offset for each IO.
350 For instance, using rw=write:4k will skip 4k for every
351 write. It turns sequential IO into sequential IO with holes.
352 See the 'rw_sequencer' option.
354 rw_sequencer=str If an offset modifier is given by appending a number to
355 the rw=<str> line, then this option controls how that
356 number modifies the IO offset being generated. Accepted
359 sequential Generate sequential offset
360 identical Generate the same offset
362 'sequential' is only useful for random IO, where fio would
363 normally generate a new random offset for every IO. If you
364 append eg 8 to randread, you would get a new random offset for
365 every 8 IO's. The result would be a seek for only every 8
366 IO's, instead of for every IO. Use rw=randread:8 to specify
367 that. As sequential IO is already sequential, setting
368 'sequential' for that would not result in any differences.
369 'identical' behaves in a similar fashion, except it sends
370 the same offset 8 number of times before generating a new
373 kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024.
374 Storage manufacturers like to use 10^3 or 1000 as a base
375 ten unit instead, for obvious reasons. Allow values are
376 1024 or 1000, with 1024 being the default.
378 unified_rw_reporting=bool Fio normally reports statistics on a per
379 data direction basis, meaning that read, write, and trim are
380 accounted and reported separately. If this option is set,
381 the fio will sum the results and report them as "mixed"
384 randrepeat=bool For random IO workloads, seed the generator in a predictable
385 way so that results are repeatable across repetitions.
387 use_os_rand=bool Fio can either use the random generator supplied by the OS
388 to generator random offsets, or it can use it's own internal
389 generator (based on Tausworthe). Default is to use the
390 internal generator, which is often of better quality and
393 fallocate=str Whether pre-allocation is performed when laying down files.
396 none Do not pre-allocate space
397 posix Pre-allocate via posix_fallocate()
398 keep Pre-allocate via fallocate() with
399 FALLOC_FL_KEEP_SIZE set
400 0 Backward-compatible alias for 'none'
401 1 Backward-compatible alias for 'posix'
403 May not be available on all supported platforms. 'keep' is only
404 available on Linux.If using ZFS on Solaris this must be set to
405 'none' because ZFS doesn't support it. Default: 'posix'.
407 fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
408 on what IO patterns it is likely to issue. Sometimes you
409 want to test specific IO patterns without telling the
410 kernel about it, in which case you can disable this option.
411 If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
412 IO and POSIX_FADV_RANDOM for random IO.
414 size=int The total size of file io for this job. Fio will run until
415 this many bytes has been transferred, unless runtime is
416 limited by other options (such as 'runtime', for instance).
417 Unless specific nrfiles and filesize options are given,
418 fio will divide this size between the available files
419 specified by the job. If not set, fio will use the full
420 size of the given files or devices. If the the files
421 do not exist, size must be given. It is also possible to
422 give size as a percentage between 1 and 100. If size=20%
423 is given, fio will use 20% of the full size of the given
426 filesize=int Individual file sizes. May be a range, in which case fio
427 will select sizes for files at random within the given range
428 and limited to 'size' in total (if that is given). If not
429 given, each created file is the same size.
432 fill_fs=bool Sets size to something really large and waits for ENOSPC (no
433 space left on device) as the terminating condition. Only makes
434 sense with sequential write. For a read workload, the mount
435 point will be filled first then IO started on the result. This
436 option doesn't make sense if operating on a raw device node,
437 since the size of that is already known by the file system.
438 Additionally, writing beyond end-of-device will not return
442 bs=int The block size used for the io units. Defaults to 4k. Values
443 can be given for both read and writes. If a single int is
444 given, it will apply to both. If a second int is specified
445 after a comma, it will apply to writes only. In other words,
446 the format is either bs=read_and_write or bs=read,write,trim.
447 bs=4k,8k will thus use 4k blocks for reads, 8k blocks for
448 writes, and 8k for trims. You can terminate the list with
449 a trailing comma. bs=4k,8k, would use the default value for
450 trims.. If you only wish to set the write size, you
451 can do so by passing an empty read size - bs=,8k will set
452 8k for writes and leave the read default value.
455 ba=int At what boundary to align random IO offsets. Defaults to
456 the same as 'blocksize' the minimum blocksize given.
457 Minimum alignment is typically 512b for using direct IO,
458 though it usually depends on the hardware block size. This
459 option is mutually exclusive with using a random map for
460 files, so it will turn off that option.
462 blocksize_range=irange
463 bsrange=irange Instead of giving a single block size, specify a range
464 and fio will mix the issued io block sizes. The issued
465 io unit will always be a multiple of the minimum value
466 given (also see bs_unaligned). Applies to both reads and
467 writes, however a second range can be given after a comma.
470 bssplit=str Sometimes you want even finer grained control of the
471 block sizes issued, not just an even split between them.
472 This option allows you to weight various block sizes,
473 so that you are able to define a specific amount of
474 block sizes issued. The format for this option is:
476 bssplit=blocksize/percentage:blocksize/percentage
478 for as many block sizes as needed. So if you want to define
479 a workload that has 50% 64k blocks, 10% 4k blocks, and
480 40% 32k blocks, you would write:
482 bssplit=4k/10:64k/50:32k/40
484 Ordering does not matter. If the percentage is left blank,
485 fio will fill in the remaining values evenly. So a bssplit
486 option like this one:
488 bssplit=4k/50:1k/:32k/
490 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
491 always add up to 100, if bssplit is given a range that adds
492 up to more, it will error out.
494 bssplit also supports giving separate splits to reads and
495 writes. The format is identical to what bs= accepts. You
496 have to separate the read and write parts with a comma. So
497 if you want a workload that has 50% 2k reads and 50% 4k reads,
498 while having 90% 4k writes and 10% 8k writes, you would
501 bssplit=2k/50:4k/50,4k/90,8k/10
504 bs_unaligned If this option is given, any byte size value within bsrange
505 may be used as a block range. This typically wont work with
506 direct IO, as that normally requires sector alignment.
508 bs_is_seq_rand If this option is set, fio will use the normal read,write
509 blocksize settings as sequential,random instead. Any random
510 read or write will use the WRITE blocksize settings, and any
511 sequential read or write will use the READ blocksize setting.
513 zero_buffers If this option is given, fio will init the IO buffers to
514 all zeroes. The default is to fill them with random data.
516 refill_buffers If this option is given, fio will refill the IO buffers
517 on every submit. The default is to only fill it at init
518 time and reuse that data. Only makes sense if zero_buffers
519 isn't specified, naturally. If data verification is enabled,
520 refill_buffers is also automatically enabled.
522 scramble_buffers=bool If refill_buffers is too costly and the target is
523 using data deduplication, then setting this option will
524 slightly modify the IO buffer contents to defeat normal
525 de-dupe attempts. This is not enough to defeat more clever
526 block compression attempts, but it will stop naive dedupe of
527 blocks. Default: true.
529 buffer_compress_percentage=int If this is set, then fio will attempt to
530 provide IO buffer content (on WRITEs) that compress to
531 the specified level. Fio does this by providing a mix of
532 random data and zeroes. Note that this is per block size
533 unit, for file/disk wide compression level that matches
534 this setting, you'll also want to set refill_buffers.
536 buffer_compress_chunk=int See buffer_compress_percentage. This
537 setting allows fio to manage how big the ranges of random
538 data and zeroed data is. Without this set, fio will
539 provide buffer_compress_percentage of blocksize random
540 data, followed by the remaining zeroed. With this set
541 to some chunk size smaller than the block size, fio can
542 alternate random and zeroed data throughout the IO
545 nrfiles=int Number of files to use for this job. Defaults to 1.
547 openfiles=int Number of files to keep open at the same time. Defaults to
548 the same as nrfiles, can be set smaller to limit the number
551 file_service_type=str Defines how fio decides which file from a job to
552 service next. The following types are defined:
554 random Just choose a file at random.
556 roundrobin Round robin over open files. This
559 sequential Finish one file before moving on to
560 the next. Multiple files can still be
561 open depending on 'openfiles'.
563 The string can have a number appended, indicating how
564 often to switch to a new file. So if option random:4 is
565 given, fio will switch to a new random file after 4 ios
568 ioengine=str Defines how the job issues io to the file. The following
571 sync Basic read(2) or write(2) io. lseek(2) is
572 used to position the io location.
574 psync Basic pread(2) or pwrite(2) io.
576 vsync Basic readv(2) or writev(2) IO.
578 psyncv Basic preadv(2) or pwritev(2) IO.
580 libaio Linux native asynchronous io. Note that Linux
581 may only support queued behaviour with
582 non-buffered IO (set direct=1 or buffered=0).
583 This engine defines engine specific options.
585 posixaio glibc posix asynchronous io.
587 solarisaio Solaris native asynchronous io.
589 windowsaio Windows native asynchronous io.
591 mmap File is memory mapped and data copied
592 to/from using memcpy(3).
594 splice splice(2) is used to transfer the data and
595 vmsplice(2) to transfer data from user
598 syslet-rw Use the syslet system calls to make
599 regular read/write async.
601 sg SCSI generic sg v3 io. May either be
602 synchronous using the SG_IO ioctl, or if
603 the target is an sg character device
604 we use read(2) and write(2) for asynchronous
607 null Doesn't transfer any data, just pretends
608 to. This is mainly used to exercise fio
609 itself and for debugging/testing purposes.
611 net Transfer over the network to given host:port.
612 Depending on the protocol used, the hostname,
613 port, listen and filename options are used to
614 specify what sort of connection to make, while
615 the protocol option determines which protocol
617 This engine defines engine specific options.
619 netsplice Like net, but uses splice/vmsplice to
620 map data and send/receive.
621 This engine defines engine specific options.
623 cpuio Doesn't transfer any data, but burns CPU
624 cycles according to the cpuload= and
625 cpucycle= options. Setting cpuload=85
626 will cause that job to do nothing but burn
627 85% of the CPU. In case of SMP machines,
628 use numjobs=<no_of_cpu> to get desired CPU
629 usage, as the cpuload only loads a single
630 CPU at the desired rate.
632 guasi The GUASI IO engine is the Generic Userspace
633 Asyncronous Syscall Interface approach
636 http://www.xmailserver.org/guasi-lib.html
638 for more info on GUASI.
640 rdma The RDMA I/O engine supports both RDMA
641 memory semantics (RDMA_WRITE/RDMA_READ) and
642 channel semantics (Send/Recv) for the
643 InfiniBand, RoCE and iWARP protocols.
645 falloc IO engine that does regular fallocate to
646 simulate data transfer as fio ioengine.
647 DDIR_READ does fallocate(,mode = keep_size,)
648 DDIR_WRITE does fallocate(,mode = 0)
649 DDIR_TRIM does fallocate(,mode = punch_hole)
651 e4defrag IO engine that does regular EXT4_IOC_MOVE_EXT
652 ioctls to simulate defragment activity in
653 request to DDIR_WRITE event
655 external Prefix to specify loading an external
656 IO engine object file. Append the engine
657 filename, eg ioengine=external:/tmp/foo.o
658 to load ioengine foo.o in /tmp.
660 iodepth=int This defines how many io units to keep in flight against
661 the file. The default is 1 for each file defined in this
662 job, can be overridden with a larger value for higher
663 concurrency. Note that increasing iodepth beyond 1 will not
664 affect synchronous ioengines (except for small degress when
665 verify_async is in use). Even async engines may impose OS
666 restrictions causing the desired depth not to be achieved.
667 This may happen on Linux when using libaio and not setting
668 direct=1, since buffered IO is not async on that OS. Keep an
669 eye on the IO depth distribution in the fio output to verify
670 that the achieved depth is as expected. Default: 1.
672 iodepth_batch_submit=int
673 iodepth_batch=int This defines how many pieces of IO to submit at once.
674 It defaults to 1 which means that we submit each IO
675 as soon as it is available, but can be raised to submit
676 bigger batches of IO at the time.
678 iodepth_batch_complete=int This defines how many pieces of IO to retrieve
679 at once. It defaults to 1 which means that we'll ask
680 for a minimum of 1 IO in the retrieval process from
681 the kernel. The IO retrieval will go on until we
682 hit the limit set by iodepth_low. If this variable is
683 set to 0, then fio will always check for completed
684 events before queuing more IO. This helps reduce
685 IO latency, at the cost of more retrieval system calls.
687 iodepth_low=int The low water mark indicating when to start filling
688 the queue again. Defaults to the same as iodepth, meaning
689 that fio will attempt to keep the queue full at all times.
690 If iodepth is set to eg 16 and iodepth_low is set to 4, then
691 after fio has filled the queue of 16 requests, it will let
692 the depth drain down to 4 before starting to fill it again.
694 direct=bool If value is true, use non-buffered io. This is usually
695 O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
696 On Windows the synchronous ioengines don't support direct io.
698 atomic=bool If value is true, attempt to use atomic direct IO. Atomic
699 writes are guaranteed to be stable once acknowledged by
700 the operating system. Only Linux supports O_ATOMIC right
703 buffered=bool If value is true, use buffered io. This is the opposite
704 of the 'direct' option. Defaults to true.
706 offset=int Start io at the given offset in the file. The data before
707 the given offset will not be touched. This effectively
708 caps the file size at real_size - offset.
710 offset_increment=int If this is provided, then the real offset becomes
711 the offset + offset_increment * thread_number, where the
712 thread number is a counter that starts at 0 and is incremented
713 for each job. This option is useful if there are several jobs
714 which are intended to operate on a file in parallel in disjoint
715 segments, with even spacing between the starting points.
717 number_ios=int Fio will normally perform IOs until it has exhausted the size
718 of the region set by size=, or if it exhaust the allocated
719 time (or hits an error condition). With this setting, the
720 range/size can be set independently of the number of IOs to
721 perform. When fio reaches this number, it will exit normally
724 fsync=int If writing to a file, issue a sync of the dirty data
725 for every number of blocks given. For example, if you give
726 32 as a parameter, fio will sync the file for every 32
727 writes issued. If fio is using non-buffered io, we may
728 not sync the file. The exception is the sg io engine, which
729 synchronizes the disk cache anyway.
731 fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
733 In FreeBSD and Windows there is no fdatasync(), this falls back to
736 sync_file_range=str:val Use sync_file_range() for every 'val' number of
737 write operations. Fio will track range of writes that
738 have happened since the last sync_file_range() call. 'str'
739 can currently be one or more of:
741 wait_before SYNC_FILE_RANGE_WAIT_BEFORE
742 write SYNC_FILE_RANGE_WRITE
743 wait_after SYNC_FILE_RANGE_WAIT_AFTER
745 So if you do sync_file_range=wait_before,write:8, fio would
746 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
747 every 8 writes. Also see the sync_file_range(2) man page.
748 This option is Linux specific.
750 overwrite=bool If true, writes to a file will always overwrite existing
751 data. If the file doesn't already exist, it will be
752 created before the write phase begins. If the file exists
753 and is large enough for the specified write phase, nothing
756 end_fsync=bool If true, fsync file contents when a write stage has completed.
758 fsync_on_close=bool If true, fio will fsync() a dirty file on close.
759 This differs from end_fsync in that it will happen on every
760 file close, not just at the end of the job.
762 rwmixread=int How large a percentage of the mix should be reads.
764 rwmixwrite=int How large a percentage of the mix should be writes. If both
765 rwmixread and rwmixwrite is given and the values do not add
766 up to 100%, the latter of the two will be used to override
767 the first. This may interfere with a given rate setting,
768 if fio is asked to limit reads or writes to a certain rate.
769 If that is the case, then the distribution may be skewed.
771 random_distribution=str:float By default, fio will use a completely uniform
772 random distribution when asked to perform random IO. Sometimes
773 it is useful to skew the distribution in specific ways,
774 ensuring that some parts of the data is more hot than others.
775 fio includes the following distribution models:
777 random Uniform random distribution
778 zipf Zipf distribution
779 pareto Pareto distribution
781 When using a zipf or pareto distribution, an input value
782 is also needed to define the access pattern. For zipf, this
783 is the zipf theta. For pareto, it's the pareto power. Fio
784 includes a test program, genzipf, that can be used visualize
785 what the given input values will yield in terms of hit rates.
786 If you wanted to use zipf with a theta of 1.2, you would use
787 random_distribution=zipf:1.2 as the option. If a non-uniform
788 model is used, fio will disable use of the random map.
790 percentage_random=int For a random workload, set how big a percentage should
791 be random. This defaults to 100%, in which case the workload
792 is fully random. It can be set from anywhere from 0 to 100.
793 Setting it to 0 would make the workload fully sequential. Any
794 setting in between will result in a random mix of sequential
795 and random IO, at the given percentages. It is possible to
796 set different values for reads, writes, and trim. To do so,
797 simply use a comma separated list. See blocksize.
799 norandommap Normally fio will cover every block of the file when doing
800 random IO. If this option is given, fio will just get a
801 new random offset without looking at past io history. This
802 means that some blocks may not be read or written, and that
803 some blocks may be read/written more than once. This option
804 is mutually exclusive with verify= if and only if multiple
805 blocksizes (via bsrange=) are used, since fio only tracks
806 complete rewrites of blocks.
808 softrandommap=bool See norandommap. If fio runs with the random block map
809 enabled and it fails to allocate the map, if this option is
810 set it will continue without a random block map. As coverage
811 will not be as complete as with random maps, this option is
814 random_generator=str Fio supports the following engines for generating
815 IO offsets for random IO:
817 tausworthe Strong 2^88 cycle random number generator
818 lfsr Linear feedback shift register generator
820 Tausworthe is a strong random number generator, but it
821 requires tracking on the side if we want to ensure that
822 blocks are only read or written once. LFSR guarantees
823 that we never generate the same offset twice, and it's
824 also less computationally expensive. It's not a true
825 random generator, however, though for IO purposes it's
826 typically good enough. LFSR only works with single
827 block sizes, not with workloads that use multiple block
828 sizes. If used with such a workload, fio may read or write
829 some blocks multiple times.
831 nice=int Run the job with the given nice value. See man nice(2).
833 prio=int Set the io priority value of this job. Linux limits us to
834 a positive value between 0 and 7, with 0 being the highest.
837 prioclass=int Set the io priority class. See man ionice(1).
839 thinktime=int Stall the job x microseconds after an io has completed before
840 issuing the next. May be used to simulate processing being
841 done by an application. See thinktime_blocks and
845 Only valid if thinktime is set - pretend to spend CPU time
846 doing something with the data received, before falling back
847 to sleeping for the rest of the period specified by
851 Only valid if thinktime is set - control how many blocks
852 to issue, before waiting 'thinktime' usecs. If not set,
853 defaults to 1 which will make fio wait 'thinktime' usecs
854 after every block. This effectively makes any queue depth
855 setting redundant, since no more than 1 IO will be queued
856 before we have to complete it and do our thinktime. In
857 other words, this setting effectively caps the queue depth
858 if the latter is larger.
860 rate=int Cap the bandwidth used by this job. The number is in bytes/sec,
861 the normal suffix rules apply. You can use rate=500k to limit
862 reads and writes to 500k each, or you can specify read and
863 writes separately. Using rate=1m,500k would limit reads to
864 1MB/sec and writes to 500KB/sec. Capping only reads or
865 writes can be done with rate=,500k or rate=500k,. The former
866 will only limit writes (to 500KB/sec), the latter will only
869 ratemin=int Tell fio to do whatever it can to maintain at least this
870 bandwidth. Failing to meet this requirement, will cause
871 the job to exit. The same format as rate is used for
872 read vs write separation.
874 rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
875 as rate, just specified independently of bandwidth. If the
876 job is given a block size range instead of a fixed value,
877 the smallest block size is used as the metric. The same format
878 as rate is used for read vs write separation.
880 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
881 the job to exit. The same format as rate is used for read vs
884 latency_target=int If set, fio will attempt to find the max performance
885 point that the given workload will run at while maintaining a
886 latency below this target. The values is given in microseconds.
887 See latency_window and latency_percentile
889 latency_window=int Used with latency_target to specify the sample window
890 that the job is run at varying queue depths to test the
891 performance. The value is given in microseconds.
893 latency_percentile=float The percentage of IOs that must fall within the
894 criteria specified by latency_target and latency_window. If not
895 set, this defaults to 100.0, meaning that all IOs must be equal
896 or below to the value set by latency_target.
898 max_latency=int If set, fio will exit the job if it exceeds this maximum
899 latency. It will exit with an ETIME error.
901 ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number
904 cpumask=int Set the CPU affinity of this job. The parameter given is a
905 bitmask of allowed CPU's the job may run on. So if you want
906 the allowed CPUs to be 1 and 5, you would pass the decimal
907 value of (1 << 1 | 1 << 5), or 34. See man
908 sched_setaffinity(2). This may not work on all supported
909 operating systems or kernel versions. This option doesn't
910 work well for a higher CPU count than what you can store in
911 an integer mask, so it can only control cpus 1-32. For
912 boxes with larger CPU counts, use cpus_allowed.
914 cpus_allowed=str Controls the same options as cpumask, but it allows a text
915 setting of the permitted CPUs instead. So to use CPUs 1 and
916 5, you would specify cpus_allowed=1,5. This options also
917 allows a range of CPUs. Say you wanted a binding to CPUs
918 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15.
920 numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The
921 arguments allow comma delimited list of cpu numbers,
922 A-B ranges, or 'all'. Note, to enable numa options support,
923 fio must be built on a system with libnuma-dev(el) installed.
925 numa_mem_policy=str Set this job's memory policy and corresponding NUMA
926 nodes. Format of the argements:
928 `mode' is one of the following memory policy:
929 default, prefer, bind, interleave, local
930 For `default' and `local' memory policy, no node is
931 needed to be specified.
932 For `prefer', only one node is allowed.
933 For `bind' and `interleave', it allow comma delimited
934 list of numbers, A-B ranges, or 'all'.
936 startdelay=time Start this job the specified number of seconds after fio
937 has started. Only useful if the job file contains several
938 jobs, and you want to delay starting some jobs to a certain
941 runtime=time Tell fio to terminate processing after the specified number
942 of seconds. It can be quite hard to determine for how long
943 a specified job will run, so this parameter is handy to
944 cap the total runtime to a given time.
946 time_based If set, fio will run for the duration of the runtime
947 specified even if the file(s) are completely read or
948 written. It will simply loop over the same workload
949 as many times as the runtime allows.
951 ramp_time=time If set, fio will run the specified workload for this amount
952 of time before logging any performance numbers. Useful for
953 letting performance settle before logging results, thus
954 minimizing the runtime required for stable results. Note
955 that the ramp_time is considered lead in time for a job,
956 thus it will increase the total runtime if a special timeout
957 or runtime is specified.
959 invalidate=bool Invalidate the buffer/page cache parts for this file prior
960 to starting io. Defaults to true.
962 sync=bool Use sync io for buffered writes. For the majority of the
963 io engines, this means using O_SYNC.
966 mem=str Fio can use various types of memory as the io unit buffer.
967 The allowed values are:
969 malloc Use memory from malloc(3) as the buffers.
971 shm Use shared memory as the buffers. Allocated
974 shmhuge Same as shm, but use huge pages as backing.
976 mmap Use mmap to allocate buffers. May either be
977 anonymous memory, or can be file backed if
978 a filename is given after the option. The
979 format is mem=mmap:/path/to/file.
981 mmaphuge Use a memory mapped huge file as the buffer
982 backing. Append filename after mmaphuge, ala
983 mem=mmaphuge:/hugetlbfs/file
985 The area allocated is a function of the maximum allowed
986 bs size for the job, multiplied by the io depth given. Note
987 that for shmhuge and mmaphuge to work, the system must have
988 free huge pages allocated. This can normally be checked
989 and set by reading/writing /proc/sys/vm/nr_hugepages on a
990 Linux system. Fio assumes a huge page is 4MB in size. So
991 to calculate the number of huge pages you need for a given
992 job file, add up the io depth of all jobs (normally one unless
993 iodepth= is used) and multiply by the maximum bs set. Then
994 divide that number by the huge page size. You can see the
995 size of the huge pages in /proc/meminfo. If no huge pages
996 are allocated by having a non-zero number in nr_hugepages,
997 using mmaphuge or shmhuge will fail. Also see hugepage-size.
999 mmaphuge also needs to have hugetlbfs mounted and the file
1000 location should point there. So if it's mounted in /huge,
1001 you would use mem=mmaphuge:/huge/somefile.
1003 iomem_align=int This indiciates the memory alignment of the IO memory buffers.
1004 Note that the given alignment is applied to the first IO unit
1005 buffer, if using iodepth the alignment of the following buffers
1006 are given by the bs used. In other words, if using a bs that is
1007 a multiple of the page sized in the system, all buffers will
1008 be aligned to this value. If using a bs that is not page
1009 aligned, the alignment of subsequent IO memory buffers is the
1010 sum of the iomem_align and bs used.
1013 Defines the size of a huge page. Must at least be equal
1014 to the system setting, see /proc/meminfo. Defaults to 4MB.
1015 Should probably always be a multiple of megabytes, so using
1016 hugepage-size=Xm is the preferred way to set this to avoid
1017 setting a non-pow-2 bad value.
1019 exitall When one job finishes, terminate the rest. The default is
1020 to wait for each job to finish, sometimes that is not the
1023 bwavgtime=int Average the calculated bandwidth over the given time. Value
1024 is specified in milliseconds.
1026 iopsavgtime=int Average the calculated IOPS over the given time. Value
1027 is specified in milliseconds.
1029 create_serialize=bool If true, serialize the file creating for the jobs.
1030 This may be handy to avoid interleaving of data
1031 files, which may greatly depend on the filesystem
1032 used and even the number of processors in the system.
1034 create_fsync=bool fsync the data file after creation. This is the
1037 create_on_open=bool Don't pre-setup the files for IO, just create open()
1038 when it's time to do IO to that file.
1040 create_only=bool If true, fio will only run the setup phase of the job.
1041 If files need to be laid out or updated on disk, only
1042 that will be done. The actual job contents are not
1045 pre_read=bool If this is given, files will be pre-read into memory before
1046 starting the given IO operation. This will also clear
1047 the 'invalidate' flag, since it is pointless to pre-read
1048 and then drop the cache. This will only work for IO engines
1049 that are seekable, since they allow you to read the same data
1050 multiple times. Thus it will not work on eg network or splice
1053 unlink=bool Unlink the job files when done. Not the default, as repeated
1054 runs of that job would then waste time recreating the file
1055 set again and again.
1057 loops=int Run the specified number of iterations of this job. Used
1058 to repeat the same workload a given number of times. Defaults
1061 do_verify=bool Run the verify phase after a write phase. Only makes sense if
1062 verify is set. Defaults to 1.
1064 verify=str If writing to a file, fio can verify the file contents
1065 after each iteration of the job. The allowed values are:
1067 md5 Use an md5 sum of the data area and store
1068 it in the header of each block.
1070 crc64 Use an experimental crc64 sum of the data
1071 area and store it in the header of each
1074 crc32c Use a crc32c sum of the data area and store
1075 it in the header of each block.
1077 crc32c-intel Use hardware assisted crc32c calcuation
1078 provided on SSE4.2 enabled processors. Falls
1079 back to regular software crc32c, if not
1080 supported by the system.
1082 crc32 Use a crc32 sum of the data area and store
1083 it in the header of each block.
1085 crc16 Use a crc16 sum of the data area and store
1086 it in the header of each block.
1088 crc7 Use a crc7 sum of the data area and store
1089 it in the header of each block.
1091 sha512 Use sha512 as the checksum function.
1093 sha256 Use sha256 as the checksum function.
1095 sha1 Use optimized sha1 as the checksum function.
1097 meta Write extra information about each io
1098 (timestamp, block number etc.). The block
1099 number is verified. See also verify_pattern.
1101 null Only pretend to verify. Useful for testing
1102 internals with ioengine=null, not for much
1105 This option can be used for repeated burn-in tests of a
1106 system to make sure that the written data is also
1107 correctly read back. If the data direction given is
1108 a read or random read, fio will assume that it should
1109 verify a previously written file. If the data direction
1110 includes any form of write, the verify will be of the
1113 verifysort=bool If set, fio will sort written verify blocks when it deems
1114 it faster to read them back in a sorted manner. This is
1115 often the case when overwriting an existing file, since
1116 the blocks are already laid out in the file system. You
1117 can ignore this option unless doing huge amounts of really
1118 fast IO where the red-black tree sorting CPU time becomes
1121 verify_offset=int Swap the verification header with data somewhere else
1122 in the block before writing. Its swapped back before
1125 verify_interval=int Write the verification header at a finer granularity
1126 than the blocksize. It will be written for chunks the
1127 size of header_interval. blocksize should divide this
1130 verify_pattern=str If set, fio will fill the io buffers with this
1131 pattern. Fio defaults to filling with totally random
1132 bytes, but sometimes it's interesting to fill with a known
1133 pattern for io verification purposes. Depending on the
1134 width of the pattern, fio will fill 1/2/3/4 bytes of the
1135 buffer at the time(it can be either a decimal or a hex number).
1136 The verify_pattern if larger than a 32-bit quantity has to
1137 be a hex number that starts with either "0x" or "0X". Use
1140 verify_fatal=bool Normally fio will keep checking the entire contents
1141 before quitting on a block verification failure. If this
1142 option is set, fio will exit the job on the first observed
1145 verify_dump=bool If set, dump the contents of both the original data
1146 block and the data block we read off disk to files. This
1147 allows later analysis to inspect just what kind of data
1148 corruption occurred. Off by default.
1150 verify_async=int Fio will normally verify IO inline from the submitting
1151 thread. This option takes an integer describing how many
1152 async offload threads to create for IO verification instead,
1153 causing fio to offload the duty of verifying IO contents
1154 to one or more separate threads. If using this offload
1155 option, even sync IO engines can benefit from using an
1156 iodepth setting higher than 1, as it allows them to have
1157 IO in flight while verifies are running.
1159 verify_async_cpus=str Tell fio to set the given CPU affinity on the
1160 async IO verification threads. See cpus_allowed for the
1163 verify_backlog=int Fio will normally verify the written contents of a
1164 job that utilizes verify once that job has completed. In
1165 other words, everything is written then everything is read
1166 back and verified. You may want to verify continually
1167 instead for a variety of reasons. Fio stores the meta data
1168 associated with an IO block in memory, so for large
1169 verify workloads, quite a bit of memory would be used up
1170 holding this meta data. If this option is enabled, fio
1171 will write only N blocks before verifying these blocks.
1173 verify_backlog_batch=int Control how many blocks fio will verify
1174 if verify_backlog is set. If not set, will default to
1175 the value of verify_backlog (meaning the entire queue
1176 is read back and verified). If verify_backlog_batch is
1177 less than verify_backlog then not all blocks will be verified,
1178 if verify_backlog_batch is larger than verify_backlog, some
1179 blocks will be verified more than once.
1182 wait_for_previous Wait for preceding jobs in the job file to exit, before
1183 starting this one. Can be used to insert serialization
1184 points in the job file. A stone wall also implies starting
1185 a new reporting group.
1187 new_group Start a new reporting group. See: group_reporting.
1189 numjobs=int Create the specified number of clones of this job. May be
1190 used to setup a larger number of threads/processes doing
1191 the same thing. Each thread is reported separately; to see
1192 statistics for all clones as a whole, use group_reporting in
1193 conjunction with new_group.
1195 group_reporting It may sometimes be interesting to display statistics for
1196 groups of jobs as a whole instead of for each individual job.
1197 This is especially true if 'numjobs' is used; looking at
1198 individual thread/process output quickly becomes unwieldy.
1199 To see the final report per-group instead of per-job, use
1200 'group_reporting'. Jobs in a file will be part of the same
1201 reporting group, unless if separated by a stonewall, or by
1204 thread fio defaults to forking jobs, however if this option is
1205 given, fio will use pthread_create(3) to create threads
1208 zonesize=int Divide a file into zones of the specified size. See zoneskip.
1210 zoneskip=int Skip the specified number of bytes when zonesize data has
1211 been read. The two zone options can be used to only do
1212 io on zones of a file.
1214 write_iolog=str Write the issued io patterns to the specified file. See
1215 read_iolog. Specify a separate file for each job, otherwise
1216 the iologs will be interspersed and the file may be corrupt.
1218 read_iolog=str Open an iolog with the specified file name and replay the
1219 io patterns it contains. This can be used to store a
1220 workload and replay it sometime later. The iolog given
1221 may also be a blktrace binary file, which allows fio
1222 to replay a workload captured by blktrace. See blktrace
1223 for how to capture such logging data. For blktrace replay,
1224 the file needs to be turned into a blkparse binary data
1225 file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
1227 replay_no_stall=int When replaying I/O with read_iolog the default behavior
1228 is to attempt to respect the time stamps within the log and
1229 replay them with the appropriate delay between IOPS. By
1230 setting this variable fio will not respect the timestamps and
1231 attempt to replay them as fast as possible while still
1232 respecting ordering. The result is the same I/O pattern to a
1233 given device, but different timings.
1235 replay_redirect=str While replaying I/O patterns using read_iolog the
1236 default behavior is to replay the IOPS onto the major/minor
1237 device that each IOP was recorded from. This is sometimes
1238 undesirable because on a different machine those major/minor
1239 numbers can map to a different device. Changing hardware on
1240 the same system can also result in a different major/minor
1241 mapping. Replay_redirect causes all IOPS to be replayed onto
1242 the single specified device regardless of the device it was
1243 recorded from. i.e. replay_redirect=/dev/sdc would cause all
1244 IO in the blktrace to be replayed onto /dev/sdc. This means
1245 multiple devices will be replayed onto a single, if the trace
1246 contains multiple devices. If you want multiple devices to be
1247 replayed concurrently to multiple redirected devices you must
1248 blkparse your trace into separate traces and replay them with
1249 independent fio invocations. Unfortuantely this also breaks
1250 the strict time ordering between multiple device accesses.
1252 write_bw_log=str If given, write a bandwidth log of the jobs in this job
1253 file. Can be used to store data of the bandwidth of the
1254 jobs in their lifetime. The included fio_generate_plots
1255 script uses gnuplot to turn these text files into nice
1256 graphs. See write_lat_log for behaviour of given
1257 filename. For this option, the suffix is _bw.log.
1259 write_lat_log=str Same as write_bw_log, except that this option stores io
1260 submission, completion, and total latencies instead. If no
1261 filename is given with this option, the default filename of
1262 "jobname_type.log" is used. Even if the filename is given,
1263 fio will still append the type of log. So if one specifies
1267 The actual log names will be foo_slat.log, foo_clat.log,
1268 and foo_lat.log. This helps fio_generate_plot fine the logs
1271 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
1272 given with this option, the default filename of
1273 "jobname_type.log" is used. Even if the filename is given,
1274 fio will still append the type of log.
1276 log_avg_msec=int By default, fio will log an entry in the iops, latency,
1277 or bw log for every IO that completes. When writing to the
1278 disk log, that can quickly grow to a very large size. Setting
1279 this option makes fio average the each log entry over the
1280 specified period of time, reducing the resolution of the log.
1283 lockmem=int Pin down the specified amount of memory with mlock(2). Can
1284 potentially be used instead of removing memory or booting
1285 with less memory to simulate a smaller amount of memory.
1286 The amount specified is per worker.
1288 exec_prerun=str Before running this job, issue the command specified
1289 through system(3). Output is redirected in a file called
1292 exec_postrun=str After the job completes, issue the command specified
1293 though system(3). Output is redirected in a file called
1294 jobname.postrun.txt.
1296 ioscheduler=str Attempt to switch the device hosting the file to the specified
1297 io scheduler before running.
1299 disk_util=bool Generate disk utilization statistics, if the platform
1300 supports it. Defaults to on.
1302 disable_lat=bool Disable measurements of total latency numbers. Useful
1303 only for cutting back the number of calls to gettimeofday,
1304 as that does impact performance at really high IOPS rates.
1305 Note that to really get rid of a large amount of these
1306 calls, this option must be used with disable_slat and
1309 disable_clat=bool Disable measurements of completion latency numbers. See
1312 disable_slat=bool Disable measurements of submission latency numbers. See
1315 disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
1318 clat_percentiles=bool Enable the reporting of percentiles of
1319 completion latencies.
1321 percentile_list=float_list Overwrite the default list of percentiles
1322 for completion latencies. Each number is a floating
1323 number in the range (0,100], and the maximum length of
1324 the list is 20. Use ':' to separate the numbers, and
1325 list the numbers in ascending order. For example,
1326 --percentile_list=99.5:99.9 will cause fio to report
1327 the values of completion latency below which 99.5% and
1328 99.9% of the observed latencies fell, respectively.
1330 clocksource=str Use the given clocksource as the base of timing. The
1331 supported options are:
1333 gettimeofday gettimeofday(2)
1335 clock_gettime clock_gettime(2)
1337 cpu Internal CPU clock source
1339 cpu is the preferred clocksource if it is reliable, as it
1340 is very fast (and fio is heavy on time calls). Fio will
1341 automatically use this clocksource if it's supported and
1342 considered reliable on the system it is running on, unless
1343 another clocksource is specifically set. For x86/x86-64 CPUs,
1344 this means supporting TSC Invariant.
1346 gtod_reduce=bool Enable all of the gettimeofday() reducing options
1347 (disable_clat, disable_slat, disable_bw) plus reduce
1348 precision of the timeout somewhat to really shrink
1349 the gettimeofday() call count. With this option enabled,
1350 we only do about 0.4% of the gtod() calls we would have
1351 done if all time keeping was enabled.
1353 gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of
1354 execution to just getting the current time. Fio (and
1355 databases, for instance) are very intensive on gettimeofday()
1356 calls. With this option, you can set one CPU aside for
1357 doing nothing but logging current time to a shared memory
1358 location. Then the other threads/processes that run IO
1359 workloads need only copy that segment, instead of entering
1360 the kernel with a gettimeofday() call. The CPU set aside
1361 for doing these time calls will be excluded from other
1362 uses. Fio will manually clear it from the CPU mask of other
1365 continue_on_error=str Normally fio will exit the job on the first observed
1366 failure. If this option is set, fio will continue the job when
1367 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
1368 is exceeded or the I/O size specified is completed. If this
1369 option is used, there are two more stats that are appended,
1370 the total error count and the first error. The error field
1371 given in the stats is the first error that was hit during the
1374 The allowed values are:
1376 none Exit on any IO or verify errors.
1378 read Continue on read errors, exit on all others.
1380 write Continue on write errors, exit on all others.
1382 io Continue on any IO error, exit on all others.
1384 verify Continue on verify errors, exit on all others.
1386 all Continue on all errors.
1388 0 Backward-compatible alias for 'none'.
1390 1 Backward-compatible alias for 'all'.
1392 ignore_error=str Sometimes you want to ignore some errors during test
1393 in that case you can specify error list for each error type.
1394 ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
1395 errors for given error type is separated with ':'. Error
1396 may be symbol ('ENOSPC', 'ENOMEM') or integer.
1398 ignore_error=EAGAIN,ENOSPC:122
1399 This option will ignore EAGAIN from READ, and ENOSPC and
1400 122(EDQUOT) from WRITE.
1402 error_dump=bool If set dump every error even if it is non fatal, true
1403 by default. If disabled only fatal error will be dumped
1405 cgroup=str Add job to this control group. If it doesn't exist, it will
1406 be created. The system must have a mounted cgroup blkio
1407 mount point for this to work. If your system doesn't have it
1408 mounted, you can do so with:
1410 # mount -t cgroup -o blkio none /cgroup
1412 cgroup_weight=int Set the weight of the cgroup to this value. See
1413 the documentation that comes with the kernel, allowed values
1414 are in the range of 100..1000.
1416 cgroup_nodelete=bool Normally fio will delete the cgroups it has created after
1417 the job completion. To override this behavior and to leave
1418 cgroups around after the job completion, set cgroup_nodelete=1.
1419 This can be useful if one wants to inspect various cgroup
1420 files after job completion. Default: false
1422 uid=int Instead of running as the invoking user, set the user ID to
1423 this value before the thread/process does any work.
1425 gid=int Set group ID, see uid.
1427 flow_id=int The ID of the flow. If not specified, it defaults to being a
1428 global flow. See flow.
1430 flow=int Weight in token-based flow control. If this value is used, then
1431 there is a 'flow counter' which is used to regulate the
1432 proportion of activity between two or more jobs. fio attempts
1433 to keep this flow counter near zero. The 'flow' parameter
1434 stands for how much should be added or subtracted to the flow
1435 counter on each iteration of the main I/O loop. That is, if
1436 one job has flow=8 and another job has flow=-1, then there
1437 will be a roughly 1:8 ratio in how much one runs vs the other.
1439 flow_watermark=int The maximum value that the absolute value of the flow
1440 counter is allowed to reach before the job must wait for a
1441 lower value of the counter.
1443 flow_sleep=int The period of time, in microseconds, to wait after the flow
1444 watermark has been exceeded before retrying operations
1446 In addition, there are some parameters which are only valid when a specific
1447 ioengine is in use. These are used identically to normal parameters, with the
1448 caveat that when used on the command line, they must come after the ioengine
1449 that defines them is selected.
1451 [libaio] userspace_reap Normally, with the libaio engine in use, fio will use
1452 the io_getevents system call to reap newly returned events.
1453 With this flag turned on, the AIO ring will be read directly
1454 from user-space to reap events. The reaping mode is only
1455 enabled when polling for a minimum of 0 events (eg when
1456 iodepth_batch_complete=0).
1458 [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles.
1460 [cpu] cpuchunks=int Split the load into cycles of the given time. In
1463 [netsplice] hostname=str
1464 [net] hostname=str The host name or IP address to use for TCP or UDP based IO.
1465 If the job is a TCP listener or UDP reader, the hostname is not
1466 used and must be omitted unless it is a valid UDP multicast
1469 [netsplice] port=int
1470 [net] port=int The TCP or UDP port to bind to or connect to.
1472 [netsplice] interface=str
1473 [net] interface=str The IP address of the network interface used to send or
1474 receive UDP multicast
1477 [net] ttl=int Time-to-live value for outgoing UDP multicast packets.
1480 [netsplice] nodelay=bool
1481 [net] nodelay=bool Set TCP_NODELAY on TCP connections.
1483 [netsplice] protocol=str
1484 [netsplice] proto=str
1486 [net] proto=str The network protocol to use. Accepted values are:
1488 tcp Transmission control protocol
1489 udp User datagram protocol
1490 unix UNIX domain socket
1492 When the protocol is TCP or UDP, the port must also be given,
1493 as well as the hostname if the job is a TCP listener or UDP
1494 reader. For unix sockets, the normal filename option should be
1495 used and the port is invalid.
1497 [net] listen For TCP network connections, tell fio to listen for incoming
1498 connections rather than initiating an outgoing connection. The
1499 hostname must be omitted if this option is used.
1500 [net] pingpong Normaly a network writer will just continue writing data, and
1501 a network reader will just consume packages. If pingpong=1
1502 is set, a writer will send its normal payload to the reader,
1503 then wait for the reader to send the same payload back. This
1504 allows fio to measure network latencies. The submission
1505 and completion latencies then measure local time spent
1506 sending or receiving, and the completion latency measures
1507 how long it took for the other end to receive and send back.
1508 For UDP multicast traffic pingpong=1 should only be set for a
1509 single reader when multiple readers are listening to the same
1512 [e4defrag] donorname=str
1513 File will be used as a block donor(swap extents between files)
1514 [e4defrag] inplace=int
1515 Configure donor file blocks allocation strategy
1516 0(default): Preallocate donor's file on init
1517 1 : allocate space immidietly inside defragment event,
1518 and free right after event
1522 6.0 Interpreting the output
1523 ---------------------------
1525 fio spits out a lot of output. While running, fio will display the
1526 status of the jobs created. An example of that would be:
1528 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
1530 The characters inside the square brackets denote the current status of
1531 each thread. The possible values (in typical life cycle order) are:
1535 P Thread setup, but not started.
1537 I Thread initialized, waiting or generating necessary data.
1538 p Thread running pre-reading file(s).
1539 R Running, doing sequential reads.
1540 r Running, doing random reads.
1541 W Running, doing sequential writes.
1542 w Running, doing random writes.
1543 M Running, doing mixed sequential reads/writes.
1544 m Running, doing mixed random reads/writes.
1545 F Running, currently waiting for fsync()
1546 V Running, doing verification of written data.
1547 E Thread exited, not reaped by main thread yet.
1549 X Thread reaped, exited with an error.
1550 K Thread reaped, exited due to signal.
1552 The other values are fairly self explanatory - number of threads
1553 currently running and doing io, rate of io since last check (read speed
1554 listed first, then write speed), and the estimated completion percentage
1555 and time for the running group. It's impossible to estimate runtime of
1556 the following groups (if any). Note that the string is displayed in order,
1557 so it's possible to tell which of the jobs are currently doing what. The
1558 first character is the first job defined in the job file, and so forth.
1560 When fio is done (or interrupted by ctrl-c), it will show the data for
1561 each thread, group of threads, and disks in that order. For each data
1562 direction, the output looks like:
1564 Client1 (g=0): err= 0:
1565 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
1566 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
1567 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
1568 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
1569 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
1570 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
1571 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1572 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1573 issued r/w: total=0/32768, short=0/0
1574 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
1575 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
1577 The client number is printed, along with the group id and error of that
1578 thread. Below is the io statistics, here for writes. In the order listed,
1581 io= Number of megabytes io performed
1582 bw= Average bandwidth rate
1583 iops= Average IOs performed per second
1584 runt= The runtime of that thread
1585 slat= Submission latency (avg being the average, stdev being the
1586 standard deviation). This is the time it took to submit
1587 the io. For sync io, the slat is really the completion
1588 latency, since queue/complete is one operation there. This
1589 value can be in milliseconds or microseconds, fio will choose
1590 the most appropriate base and print that. In the example
1591 above, milliseconds is the best scale. Note: in --minimal mode
1592 latencies are always expressed in microseconds.
1593 clat= Completion latency. Same names as slat, this denotes the
1594 time from submission to completion of the io pieces. For
1595 sync io, clat will usually be equal (or very close) to 0,
1596 as the time from submit to complete is basically just
1597 CPU time (io has already been done, see slat explanation).
1598 bw= Bandwidth. Same names as the xlat stats, but also includes
1599 an approximate percentage of total aggregate bandwidth
1600 this thread received in this group. This last value is
1601 only really useful if the threads in this group are on the
1602 same disk, since they are then competing for disk access.
1603 cpu= CPU usage. User and system time, along with the number
1604 of context switches this thread went through, usage of
1605 system and user time, and finally the number of major
1606 and minor page faults.
1607 IO depths= The distribution of io depths over the job life time. The
1608 numbers are divided into powers of 2, so for example the
1609 16= entries includes depths up to that value but higher
1610 than the previous entry. In other words, it covers the
1611 range from 16 to 31.
1612 IO submit= How many pieces of IO were submitting in a single submit
1613 call. Each entry denotes that amount and below, until
1614 the previous entry - eg, 8=100% mean that we submitted
1615 anywhere in between 5-8 ios per submit call.
1616 IO complete= Like the above submit number, but for completions instead.
1617 IO issued= The number of read/write requests issued, and how many
1619 IO latencies= The distribution of IO completion latencies. This is the
1620 time from when IO leaves fio and when it gets completed.
1621 The numbers follow the same pattern as the IO depths,
1622 meaning that 2=1.6% means that 1.6% of the IO completed
1623 within 2 msecs, 20=12.8% means that 12.8% of the IO
1624 took more than 10 msecs, but less than (or equal to) 20 msecs.
1626 After each client has been listed, the group statistics are printed. They
1627 will look like this:
1629 Run status group 0 (all jobs):
1630 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
1631 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
1633 For each data direction, it prints:
1635 io= Number of megabytes io performed.
1636 aggrb= Aggregate bandwidth of threads in this group.
1637 minb= The minimum average bandwidth a thread saw.
1638 maxb= The maximum average bandwidth a thread saw.
1639 mint= The smallest runtime of the threads in that group.
1640 maxt= The longest runtime of the threads in that group.
1642 And finally, the disk statistics are printed. They will look like this:
1644 Disk stats (read/write):
1645 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
1647 Each value is printed for both reads and writes, with reads first. The
1650 ios= Number of ios performed by all groups.
1651 merge= Number of merges io the io scheduler.
1652 ticks= Number of ticks we kept the disk busy.
1653 io_queue= Total time spent in the disk queue.
1654 util= The disk utilization. A value of 100% means we kept the disk
1655 busy constantly, 50% would be a disk idling half of the time.
1657 It is also possible to get fio to dump the current output while it is
1658 running, without terminating the job. To do that, send fio the USR1 signal.
1659 You can also get regularly timed dumps by using the --status-interval
1660 parameter, or by creating a file in /tmp named fio-dump-status. If fio
1661 sees this file, it will unlink it and dump the current output status.
1667 For scripted usage where you typically want to generate tables or graphs
1668 of the results, fio can output the results in a semicolon separated format.
1669 The format is one long line of values, such as:
1671 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
1672 A description of this job goes here.
1674 The job description (if provided) follows on a second line.
1676 To enable terse output, use the --minimal command line option. The first
1677 value is the version of the terse output format. If the output has to
1678 be changed for some reason, this number will be incremented by 1 to
1679 signify that change.
1681 Split up, the format is as follows:
1683 terse version, fio version, jobname, groupid, error
1685 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
1686 Submission latency: min, max, mean, deviation (usec)
1687 Completion latency: min, max, mean, deviation (usec)
1688 Completion latency percentiles: 20 fields (see below)
1689 Total latency: min, max, mean, deviation (usec)
1690 Bw (KB/s): min, max, aggregate percentage of total, mean, deviation
1692 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
1693 Submission latency: min, max, mean, deviation (usec)
1694 Completion latency: min, max, mean, deviation (usec)
1695 Completion latency percentiles: 20 fields (see below)
1696 Total latency: min, max, mean, deviation (usec)
1697 Bw (KB/s): min, max, aggregate percentage of total, mean, deviation
1698 CPU usage: user, system, context switches, major faults, minor faults
1699 IO depths: <=1, 2, 4, 8, 16, 32, >=64
1700 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
1701 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
1702 Disk utilization: Disk name, Read ios, write ios,
1703 Read merges, write merges,
1704 Read ticks, write ticks,
1705 Time spent in queue, disk utilization percentage
1706 Additional Info (dependent on continue_on_error, default off): total # errors, first error code
1708 Additional Info (dependent on description being set): Text description
1710 Completion latency percentiles can be a grouping of up to 20 sets, so
1711 for the terse output fio writes all of them. Each field will look like this:
1715 which is the Xth percentile, and the usec latency associated with it.
1717 For disk utilization, all disks used by fio are shown. So for each disk
1718 there will be a disk utilization section.
1721 8.0 Trace file format
1722 ---------------------
1723 There are two trace file format that you can encounter. The older (v1) format
1724 is unsupported since version 1.20-rc3 (March 2008). It will still be described
1725 below in case that you get an old trace and want to understand it.
1727 In any case the trace is a simple text file with a single action per line.
1730 8.1 Trace file format v1
1731 ------------------------
1732 Each line represents a single io action in the following format:
1736 where rw=0/1 for read/write, and the offset and length entries being in bytes.
1738 This format is not supported in Fio versions => 1.20-rc3.
1741 8.2 Trace file format v2
1742 ------------------------
1743 The second version of the trace file format was added in Fio version 1.17.
1744 It allows to access more then one file per trace and has a bigger set of
1745 possible file actions.
1747 The first line of the trace file has to be:
1751 Following this can be lines in two different formats, which are described below.
1753 The file management format:
1757 The filename is given as an absolute path. The action can be one of these:
1759 add Add the given filename to the trace
1760 open Open the file with the given filename. The filename has to have
1761 been added with the add action before.
1762 close Close the file with the given filename. The file has to have been
1766 The file io action format:
1768 filename action offset length
1770 The filename is given as an absolute path, and has to have been added and opened
1771 before it can be used with this format. The offset and length are given in
1772 bytes. The action can be one of these:
1774 wait Wait for 'offset' microseconds. Everything below 100 is discarded.
1775 read Read 'length' bytes beginning from 'offset'
1776 write Write 'length' bytes beginning from 'offset'
1777 sync fsync() the file
1778 datasync fdatasync() the file
1779 trim trim the given file from the given 'offset' for 'length' bytes
1782 9.0 CPU idleness profiling
1783 --------------------------
1784 In some cases, we want to understand CPU overhead in a test. For example,
1785 we test patches for the specific goodness of whether they reduce CPU usage.
1786 fio implements a balloon approach to create a thread per CPU that runs at
1787 idle priority, meaning that it only runs when nobody else needs the cpu.
1788 By measuring the amount of work completed by the thread, idleness of each
1789 CPU can be derived accordingly.
1791 An unit work is defined as touching a full page of unsigned characters. Mean
1792 and standard deviation of time to complete an unit work is reported in "unit
1793 work" section. Options can be chosen to report detailed percpu idleness or
1794 overall system idleness by aggregating percpu stats.
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