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.
447 bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
448 for writes. If you only wish to set the write size, you
449 can do so by passing an empty read size - bs=,8k will set
450 8k for writes and leave the read default value.
453 ba=int At what boundary to align random IO offsets. Defaults to
454 the same as 'blocksize' the minimum blocksize given.
455 Minimum alignment is typically 512b for using direct IO,
456 though it usually depends on the hardware block size. This
457 option is mutually exclusive with using a random map for
458 files, so it will turn off that option.
460 blocksize_range=irange
461 bsrange=irange Instead of giving a single block size, specify a range
462 and fio will mix the issued io block sizes. The issued
463 io unit will always be a multiple of the minimum value
464 given (also see bs_unaligned). Applies to both reads and
465 writes, however a second range can be given after a comma.
468 bssplit=str Sometimes you want even finer grained control of the
469 block sizes issued, not just an even split between them.
470 This option allows you to weight various block sizes,
471 so that you are able to define a specific amount of
472 block sizes issued. The format for this option is:
474 bssplit=blocksize/percentage:blocksize/percentage
476 for as many block sizes as needed. So if you want to define
477 a workload that has 50% 64k blocks, 10% 4k blocks, and
478 40% 32k blocks, you would write:
480 bssplit=4k/10:64k/50:32k/40
482 Ordering does not matter. If the percentage is left blank,
483 fio will fill in the remaining values evenly. So a bssplit
484 option like this one:
486 bssplit=4k/50:1k/:32k/
488 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
489 always add up to 100, if bssplit is given a range that adds
490 up to more, it will error out.
492 bssplit also supports giving separate splits to reads and
493 writes. The format is identical to what bs= accepts. You
494 have to separate the read and write parts with a comma. So
495 if you want a workload that has 50% 2k reads and 50% 4k reads,
496 while having 90% 4k writes and 10% 8k writes, you would
499 bssplit=2k/50:4k/50,4k/90,8k/10
502 bs_unaligned If this option is given, any byte size value within bsrange
503 may be used as a block range. This typically wont work with
504 direct IO, as that normally requires sector alignment.
506 zero_buffers If this option is given, fio will init the IO buffers to
507 all zeroes. The default is to fill them with random data.
509 refill_buffers If this option is given, fio will refill the IO buffers
510 on every submit. The default is to only fill it at init
511 time and reuse that data. Only makes sense if zero_buffers
512 isn't specified, naturally. If data verification is enabled,
513 refill_buffers is also automatically enabled.
515 scramble_buffers=bool If refill_buffers is too costly and the target is
516 using data deduplication, then setting this option will
517 slightly modify the IO buffer contents to defeat normal
518 de-dupe attempts. This is not enough to defeat more clever
519 block compression attempts, but it will stop naive dedupe of
520 blocks. Default: true.
522 buffer_compress_percentage=int If this is set, then fio will attempt to
523 provide IO buffer content (on WRITEs) that compress to
524 the specified level. Fio does this by providing a mix of
525 random data and zeroes. Note that this is per block size
526 unit, for file/disk wide compression level that matches
527 this setting, you'll also want to set refill_buffers.
529 buffer_compress_chunk=int See buffer_compress_percentage. This
530 setting allows fio to manage how big the ranges of random
531 data and zeroed data is. Without this set, fio will
532 provide buffer_compress_percentage of blocksize random
533 data, followed by the remaining zeroed. With this set
534 to some chunk size smaller than the block size, fio can
535 alternate random and zeroed data throughout the IO
538 nrfiles=int Number of files to use for this job. Defaults to 1.
540 openfiles=int Number of files to keep open at the same time. Defaults to
541 the same as nrfiles, can be set smaller to limit the number
544 file_service_type=str Defines how fio decides which file from a job to
545 service next. The following types are defined:
547 random Just choose a file at random.
549 roundrobin Round robin over open files. This
552 sequential Finish one file before moving on to
553 the next. Multiple files can still be
554 open depending on 'openfiles'.
556 The string can have a number appended, indicating how
557 often to switch to a new file. So if option random:4 is
558 given, fio will switch to a new random file after 4 ios
561 ioengine=str Defines how the job issues io to the file. The following
564 sync Basic read(2) or write(2) io. lseek(2) is
565 used to position the io location.
567 psync Basic pread(2) or pwrite(2) io.
569 vsync Basic readv(2) or writev(2) IO.
571 psyncv Basic preadv(2) or pwritev(2) IO.
573 libaio Linux native asynchronous io. Note that Linux
574 may only support queued behaviour with
575 non-buffered IO (set direct=1 or buffered=0).
576 This engine defines engine specific options.
578 posixaio glibc posix asynchronous io.
580 solarisaio Solaris native asynchronous io.
582 windowsaio Windows native asynchronous io.
584 mmap File is memory mapped and data copied
585 to/from using memcpy(3).
587 splice splice(2) is used to transfer the data and
588 vmsplice(2) to transfer data from user
591 syslet-rw Use the syslet system calls to make
592 regular read/write async.
594 sg SCSI generic sg v3 io. May either be
595 synchronous using the SG_IO ioctl, or if
596 the target is an sg character device
597 we use read(2) and write(2) for asynchronous
600 null Doesn't transfer any data, just pretends
601 to. This is mainly used to exercise fio
602 itself and for debugging/testing purposes.
604 net Transfer over the network to given host:port.
605 Depending on the protocol used, the hostname,
606 port, listen and filename options are used to
607 specify what sort of connection to make, while
608 the protocol option determines which protocol
610 This engine defines engine specific options.
612 netsplice Like net, but uses splice/vmsplice to
613 map data and send/receive.
614 This engine defines engine specific options.
616 cpuio Doesn't transfer any data, but burns CPU
617 cycles according to the cpuload= and
618 cpucycle= options. Setting cpuload=85
619 will cause that job to do nothing but burn
620 85% of the CPU. In case of SMP machines,
621 use numjobs=<no_of_cpu> to get desired CPU
622 usage, as the cpuload only loads a single
623 CPU at the desired rate.
625 guasi The GUASI IO engine is the Generic Userspace
626 Asyncronous Syscall Interface approach
629 http://www.xmailserver.org/guasi-lib.html
631 for more info on GUASI.
633 rdma The RDMA I/O engine supports both RDMA
634 memory semantics (RDMA_WRITE/RDMA_READ) and
635 channel semantics (Send/Recv) for the
636 InfiniBand, RoCE and iWARP protocols.
638 falloc IO engine that does regular fallocate to
639 simulate data transfer as fio ioengine.
640 DDIR_READ does fallocate(,mode = keep_size,)
641 DDIR_WRITE does fallocate(,mode = 0)
642 DDIR_TRIM does fallocate(,mode = punch_hole)
644 e4defrag IO engine that does regular EXT4_IOC_MOVE_EXT
645 ioctls to simulate defragment activity in
646 request to DDIR_WRITE event
648 external Prefix to specify loading an external
649 IO engine object file. Append the engine
650 filename, eg ioengine=external:/tmp/foo.o
651 to load ioengine foo.o in /tmp.
653 iodepth=int This defines how many io units to keep in flight against
654 the file. The default is 1 for each file defined in this
655 job, can be overridden with a larger value for higher
656 concurrency. Note that increasing iodepth beyond 1 will not
657 affect synchronous ioengines (except for small degress when
658 verify_async is in use). Even async engines may impose OS
659 restrictions causing the desired depth not to be achieved.
660 This may happen on Linux when using libaio and not setting
661 direct=1, since buffered IO is not async on that OS. Keep an
662 eye on the IO depth distribution in the fio output to verify
663 that the achieved depth is as expected. Default: 1.
665 iodepth_batch_submit=int
666 iodepth_batch=int This defines how many pieces of IO to submit at once.
667 It defaults to 1 which means that we submit each IO
668 as soon as it is available, but can be raised to submit
669 bigger batches of IO at the time.
671 iodepth_batch_complete=int This defines how many pieces of IO to retrieve
672 at once. It defaults to 1 which means that we'll ask
673 for a minimum of 1 IO in the retrieval process from
674 the kernel. The IO retrieval will go on until we
675 hit the limit set by iodepth_low. If this variable is
676 set to 0, then fio will always check for completed
677 events before queuing more IO. This helps reduce
678 IO latency, at the cost of more retrieval system calls.
680 iodepth_low=int The low water mark indicating when to start filling
681 the queue again. Defaults to the same as iodepth, meaning
682 that fio will attempt to keep the queue full at all times.
683 If iodepth is set to eg 16 and iodepth_low is set to 4, then
684 after fio has filled the queue of 16 requests, it will let
685 the depth drain down to 4 before starting to fill it again.
687 direct=bool If value is true, use non-buffered io. This is usually
688 O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
689 On Windows the synchronous ioengines don't support direct io.
691 buffered=bool If value is true, use buffered io. This is the opposite
692 of the 'direct' option. Defaults to true.
694 offset=int Start io at the given offset in the file. The data before
695 the given offset will not be touched. This effectively
696 caps the file size at real_size - offset.
698 offset_increment=int If this is provided, then the real offset becomes
699 the offset + offset_increment * thread_number, where the
700 thread number is a counter that starts at 0 and is incremented
701 for each job. This option is useful if there are several jobs
702 which are intended to operate on a file in parallel in disjoint
703 segments, with even spacing between the starting points.
705 fsync=int If writing to a file, issue a sync of the dirty data
706 for every number of blocks given. For example, if you give
707 32 as a parameter, fio will sync the file for every 32
708 writes issued. If fio is using non-buffered io, we may
709 not sync the file. The exception is the sg io engine, which
710 synchronizes the disk cache anyway.
712 fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
714 In FreeBSD and Windows there is no fdatasync(), this falls back to
717 sync_file_range=str:val Use sync_file_range() for every 'val' number of
718 write operations. Fio will track range of writes that
719 have happened since the last sync_file_range() call. 'str'
720 can currently be one or more of:
722 wait_before SYNC_FILE_RANGE_WAIT_BEFORE
723 write SYNC_FILE_RANGE_WRITE
724 wait_after SYNC_FILE_RANGE_WAIT_AFTER
726 So if you do sync_file_range=wait_before,write:8, fio would
727 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
728 every 8 writes. Also see the sync_file_range(2) man page.
729 This option is Linux specific.
731 overwrite=bool If true, writes to a file will always overwrite existing
732 data. If the file doesn't already exist, it will be
733 created before the write phase begins. If the file exists
734 and is large enough for the specified write phase, nothing
737 end_fsync=bool If true, fsync file contents when a write stage has completed.
739 fsync_on_close=bool If true, fio will fsync() a dirty file on close.
740 This differs from end_fsync in that it will happen on every
741 file close, not just at the end of the job.
743 rwmixread=int How large a percentage of the mix should be reads.
745 rwmixwrite=int How large a percentage of the mix should be writes. If both
746 rwmixread and rwmixwrite is given and the values do not add
747 up to 100%, the latter of the two will be used to override
748 the first. This may interfere with a given rate setting,
749 if fio is asked to limit reads or writes to a certain rate.
750 If that is the case, then the distribution may be skewed.
752 random_distribution=str:float By default, fio will use a completely uniform
753 random distribution when asked to perform random IO. Sometimes
754 it is useful to skew the distribution in specific ways,
755 ensuring that some parts of the data is more hot than others.
756 fio includes the following distribution models:
758 random Uniform random distribution
759 zipf Zipf distribution
760 pareto Pareto distribution
762 When using a zipf or pareto distribution, an input value
763 is also needed to define the access pattern. For zipf, this
764 is the zipf theta. For pareto, it's the pareto power. Fio
765 includes a test program, genzipf, that can be used visualize
766 what the given input values will yield in terms of hit rates.
767 If you wanted to use zipf with a theta of 1.2, you would use
768 random_distribution=zipf:1.2 as the option. If a non-uniform
769 model is used, fio will disable use of the random map.
771 percentage_random=int For a random workload, set how big a percentage should
772 be random. This defaults to 100%, in which case the workload
773 is fully random. It can be set from anywhere from 0 to 100.
774 Setting it to 0 would make the workload fully sequential. Any
775 setting in between will result in a random mix of sequential
776 and random IO, at the given percentages.
778 percentage_sequential=int See percentage_random. It is guaranteed that
779 they add up to 100. The later setting has priority, each
780 will adjust the other.
782 norandommap Normally fio will cover every block of the file when doing
783 random IO. If this option is given, fio will just get a
784 new random offset without looking at past io history. This
785 means that some blocks may not be read or written, and that
786 some blocks may be read/written more than once. This option
787 is mutually exclusive with verify= if and only if multiple
788 blocksizes (via bsrange=) are used, since fio only tracks
789 complete rewrites of blocks.
791 softrandommap=bool See norandommap. If fio runs with the random block map
792 enabled and it fails to allocate the map, if this option is
793 set it will continue without a random block map. As coverage
794 will not be as complete as with random maps, this option is
797 random_generator=str Fio supports the following engines for generating
798 IO offsets for random IO:
800 tausworthe Strong 2^88 cycle random number generator
801 lfsr Linear feedback shift register generator
803 Tausworthe is a strong random number generator, but it
804 requires tracking on the side if we want to ensure that
805 blocks are only read or written once. LFSR guarantees
806 that we never generate the same offset twice, and it's
807 also less computationally expensive. It's not a true
808 random generator, however, though for IO purposes it's
809 typically good enough. LFSR only works with single
810 block sizes, not with workloads that use multiple block
811 sizes. If used with such a workload, fio may read or write
812 some blocks multiple times.
814 nice=int Run the job with the given nice value. See man nice(2).
816 prio=int Set the io priority value of this job. Linux limits us to
817 a positive value between 0 and 7, with 0 being the highest.
820 prioclass=int Set the io priority class. See man ionice(1).
822 thinktime=int Stall the job x microseconds after an io has completed before
823 issuing the next. May be used to simulate processing being
824 done by an application. See thinktime_blocks and
828 Only valid if thinktime is set - pretend to spend CPU time
829 doing something with the data received, before falling back
830 to sleeping for the rest of the period specified by
834 Only valid if thinktime is set - control how many blocks
835 to issue, before waiting 'thinktime' usecs. If not set,
836 defaults to 1 which will make fio wait 'thinktime' usecs
839 rate=int Cap the bandwidth used by this job. The number is in bytes/sec,
840 the normal suffix rules apply. You can use rate=500k to limit
841 reads and writes to 500k each, or you can specify read and
842 writes separately. Using rate=1m,500k would limit reads to
843 1MB/sec and writes to 500KB/sec. Capping only reads or
844 writes can be done with rate=,500k or rate=500k,. The former
845 will only limit writes (to 500KB/sec), the latter will only
848 ratemin=int Tell fio to do whatever it can to maintain at least this
849 bandwidth. Failing to meet this requirement, will cause
850 the job to exit. The same format as rate is used for
851 read vs write separation.
853 rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
854 as rate, just specified independently of bandwidth. If the
855 job is given a block size range instead of a fixed value,
856 the smallest block size is used as the metric. The same format
857 as rate is used for read vs write seperation.
859 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
860 the job to exit. The same format as rate is used for read vs
863 max_latency=int If set, fio will exit the job if it exceeds this maximum
864 latency. It will exit with an ETIME error.
866 ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number
869 cpumask=int Set the CPU affinity of this job. The parameter given is a
870 bitmask of allowed CPU's the job may run on. So if you want
871 the allowed CPUs to be 1 and 5, you would pass the decimal
872 value of (1 << 1 | 1 << 5), or 34. See man
873 sched_setaffinity(2). This may not work on all supported
874 operating systems or kernel versions. This option doesn't
875 work well for a higher CPU count than what you can store in
876 an integer mask, so it can only control cpus 1-32. For
877 boxes with larger CPU counts, use cpus_allowed.
879 cpus_allowed=str Controls the same options as cpumask, but it allows a text
880 setting of the permitted CPUs instead. So to use CPUs 1 and
881 5, you would specify cpus_allowed=1,5. This options also
882 allows a range of CPUs. Say you wanted a binding to CPUs
883 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15.
885 numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The
886 arguments allow comma delimited list of cpu numbers,
887 A-B ranges, or 'all'. Note, to enable numa options support,
888 fio must be built on a system with libnuma-dev(el) installed.
890 numa_mem_policy=str Set this job's memory policy and corresponding NUMA
891 nodes. Format of the argements:
893 `mode' is one of the following memory policy:
894 default, prefer, bind, interleave, local
895 For `default' and `local' memory policy, no node is
896 needed to be specified.
897 For `prefer', only one node is allowed.
898 For `bind' and `interleave', it allow comma delimited
899 list of numbers, A-B ranges, or 'all'.
901 startdelay=time Start this job the specified number of seconds after fio
902 has started. Only useful if the job file contains several
903 jobs, and you want to delay starting some jobs to a certain
906 runtime=time Tell fio to terminate processing after the specified number
907 of seconds. It can be quite hard to determine for how long
908 a specified job will run, so this parameter is handy to
909 cap the total runtime to a given time.
911 time_based If set, fio will run for the duration of the runtime
912 specified even if the file(s) are completely read or
913 written. It will simply loop over the same workload
914 as many times as the runtime allows.
916 ramp_time=time If set, fio will run the specified workload for this amount
917 of time before logging any performance numbers. Useful for
918 letting performance settle before logging results, thus
919 minimizing the runtime required for stable results. Note
920 that the ramp_time is considered lead in time for a job,
921 thus it will increase the total runtime if a special timeout
922 or runtime is specified.
924 invalidate=bool Invalidate the buffer/page cache parts for this file prior
925 to starting io. Defaults to true.
927 sync=bool Use sync io for buffered writes. For the majority of the
928 io engines, this means using O_SYNC.
931 mem=str Fio can use various types of memory as the io unit buffer.
932 The allowed values are:
934 malloc Use memory from malloc(3) as the buffers.
936 shm Use shared memory as the buffers. Allocated
939 shmhuge Same as shm, but use huge pages as backing.
941 mmap Use mmap to allocate buffers. May either be
942 anonymous memory, or can be file backed if
943 a filename is given after the option. The
944 format is mem=mmap:/path/to/file.
946 mmaphuge Use a memory mapped huge file as the buffer
947 backing. Append filename after mmaphuge, ala
948 mem=mmaphuge:/hugetlbfs/file
950 The area allocated is a function of the maximum allowed
951 bs size for the job, multiplied by the io depth given. Note
952 that for shmhuge and mmaphuge to work, the system must have
953 free huge pages allocated. This can normally be checked
954 and set by reading/writing /proc/sys/vm/nr_hugepages on a
955 Linux system. Fio assumes a huge page is 4MB in size. So
956 to calculate the number of huge pages you need for a given
957 job file, add up the io depth of all jobs (normally one unless
958 iodepth= is used) and multiply by the maximum bs set. Then
959 divide that number by the huge page size. You can see the
960 size of the huge pages in /proc/meminfo. If no huge pages
961 are allocated by having a non-zero number in nr_hugepages,
962 using mmaphuge or shmhuge will fail. Also see hugepage-size.
964 mmaphuge also needs to have hugetlbfs mounted and the file
965 location should point there. So if it's mounted in /huge,
966 you would use mem=mmaphuge:/huge/somefile.
968 iomem_align=int This indiciates the memory alignment of the IO memory buffers.
969 Note that the given alignment is applied to the first IO unit
970 buffer, if using iodepth the alignment of the following buffers
971 are given by the bs used. In other words, if using a bs that is
972 a multiple of the page sized in the system, all buffers will
973 be aligned to this value. If using a bs that is not page
974 aligned, the alignment of subsequent IO memory buffers is the
975 sum of the iomem_align and bs used.
978 Defines the size of a huge page. Must at least be equal
979 to the system setting, see /proc/meminfo. Defaults to 4MB.
980 Should probably always be a multiple of megabytes, so using
981 hugepage-size=Xm is the preferred way to set this to avoid
982 setting a non-pow-2 bad value.
984 exitall When one job finishes, terminate the rest. The default is
985 to wait for each job to finish, sometimes that is not the
988 bwavgtime=int Average the calculated bandwidth over the given time. Value
989 is specified in milliseconds.
991 iopsavgtime=int Average the calculated IOPS over the given time. Value
992 is specified in milliseconds.
994 create_serialize=bool If true, serialize the file creating for the jobs.
995 This may be handy to avoid interleaving of data
996 files, which may greatly depend on the filesystem
997 used and even the number of processors in the system.
999 create_fsync=bool fsync the data file after creation. This is the
1002 create_on_open=bool Don't pre-setup the files for IO, just create open()
1003 when it's time to do IO to that file.
1005 create_only=bool If true, fio will only run the setup phase of the job.
1006 If files need to be laid out or updated on disk, only
1007 that will be done. The actual job contents are not
1010 pre_read=bool If this is given, files will be pre-read into memory before
1011 starting the given IO operation. This will also clear
1012 the 'invalidate' flag, since it is pointless to pre-read
1013 and then drop the cache. This will only work for IO engines
1014 that are seekable, since they allow you to read the same data
1015 multiple times. Thus it will not work on eg network or splice
1018 unlink=bool Unlink the job files when done. Not the default, as repeated
1019 runs of that job would then waste time recreating the file
1020 set again and again.
1022 loops=int Run the specified number of iterations of this job. Used
1023 to repeat the same workload a given number of times. Defaults
1026 do_verify=bool Run the verify phase after a write phase. Only makes sense if
1027 verify is set. Defaults to 1.
1029 verify=str If writing to a file, fio can verify the file contents
1030 after each iteration of the job. The allowed values are:
1032 md5 Use an md5 sum of the data area and store
1033 it in the header of each block.
1035 crc64 Use an experimental crc64 sum of the data
1036 area and store it in the header of each
1039 crc32c Use a crc32c sum of the data area and store
1040 it in the header of each block.
1042 crc32c-intel Use hardware assisted crc32c calcuation
1043 provided on SSE4.2 enabled processors. Falls
1044 back to regular software crc32c, if not
1045 supported by the system.
1047 crc32 Use a crc32 sum of the data area and store
1048 it in the header of each block.
1050 crc16 Use a crc16 sum of the data area and store
1051 it in the header of each block.
1053 crc7 Use a crc7 sum of the data area and store
1054 it in the header of each block.
1056 sha512 Use sha512 as the checksum function.
1058 sha256 Use sha256 as the checksum function.
1060 sha1 Use optimized sha1 as the checksum function.
1062 meta Write extra information about each io
1063 (timestamp, block number etc.). The block
1064 number is verified. See also verify_pattern.
1066 null Only pretend to verify. Useful for testing
1067 internals with ioengine=null, not for much
1070 This option can be used for repeated burn-in tests of a
1071 system to make sure that the written data is also
1072 correctly read back. If the data direction given is
1073 a read or random read, fio will assume that it should
1074 verify a previously written file. If the data direction
1075 includes any form of write, the verify will be of the
1078 verifysort=bool If set, fio will sort written verify blocks when it deems
1079 it faster to read them back in a sorted manner. This is
1080 often the case when overwriting an existing file, since
1081 the blocks are already laid out in the file system. You
1082 can ignore this option unless doing huge amounts of really
1083 fast IO where the red-black tree sorting CPU time becomes
1086 verify_offset=int Swap the verification header with data somewhere else
1087 in the block before writing. Its swapped back before
1090 verify_interval=int Write the verification header at a finer granularity
1091 than the blocksize. It will be written for chunks the
1092 size of header_interval. blocksize should divide this
1095 verify_pattern=str If set, fio will fill the io buffers with this
1096 pattern. Fio defaults to filling with totally random
1097 bytes, but sometimes it's interesting to fill with a known
1098 pattern for io verification purposes. Depending on the
1099 width of the pattern, fio will fill 1/2/3/4 bytes of the
1100 buffer at the time(it can be either a decimal or a hex number).
1101 The verify_pattern if larger than a 32-bit quantity has to
1102 be a hex number that starts with either "0x" or "0X". Use
1105 verify_fatal=bool Normally fio will keep checking the entire contents
1106 before quitting on a block verification failure. If this
1107 option is set, fio will exit the job on the first observed
1110 verify_dump=bool If set, dump the contents of both the original data
1111 block and the data block we read off disk to files. This
1112 allows later analysis to inspect just what kind of data
1113 corruption occurred. Off by default.
1115 verify_async=int Fio will normally verify IO inline from the submitting
1116 thread. This option takes an integer describing how many
1117 async offload threads to create for IO verification instead,
1118 causing fio to offload the duty of verifying IO contents
1119 to one or more separate threads. If using this offload
1120 option, even sync IO engines can benefit from using an
1121 iodepth setting higher than 1, as it allows them to have
1122 IO in flight while verifies are running.
1124 verify_async_cpus=str Tell fio to set the given CPU affinity on the
1125 async IO verification threads. See cpus_allowed for the
1128 verify_backlog=int Fio will normally verify the written contents of a
1129 job that utilizes verify once that job has completed. In
1130 other words, everything is written then everything is read
1131 back and verified. You may want to verify continually
1132 instead for a variety of reasons. Fio stores the meta data
1133 associated with an IO block in memory, so for large
1134 verify workloads, quite a bit of memory would be used up
1135 holding this meta data. If this option is enabled, fio
1136 will write only N blocks before verifying these blocks.
1138 will verify the previously written blocks before continuing
1141 verify_backlog_batch=int Control how many blocks fio will verify
1142 if verify_backlog is set. If not set, will default to
1143 the value of verify_backlog (meaning the entire queue
1144 is read back and verified). If verify_backlog_batch is
1145 less than verify_backlog then not all blocks will be verified,
1146 if verify_backlog_batch is larger than verify_backlog, some
1147 blocks will be verified more than once.
1150 wait_for_previous Wait for preceeding jobs in the job file to exit, before
1151 starting this one. Can be used to insert serialization
1152 points in the job file. A stone wall also implies starting
1153 a new reporting group.
1155 new_group Start a new reporting group. See: group_reporting.
1157 numjobs=int Create the specified number of clones of this job. May be
1158 used to setup a larger number of threads/processes doing
1159 the same thing. Each thread is reported separately; to see
1160 statistics for all clones as a whole, use group_reporting in
1161 conjunction with new_group.
1163 group_reporting It may sometimes be interesting to display statistics for
1164 groups of jobs as a whole instead of for each individual job.
1165 This is especially true if 'numjobs' is used; looking at
1166 individual thread/process output quickly becomes unwieldy.
1167 To see the final report per-group instead of per-job, use
1168 'group_reporting'. Jobs in a file will be part of the same
1169 reporting group, unless if separated by a stonewall, or by
1172 thread fio defaults to forking jobs, however if this option is
1173 given, fio will use pthread_create(3) to create threads
1176 zonesize=int Divide a file into zones of the specified size. See zoneskip.
1178 zoneskip=int Skip the specified number of bytes when zonesize data has
1179 been read. The two zone options can be used to only do
1180 io on zones of a file.
1182 write_iolog=str Write the issued io patterns to the specified file. See
1183 read_iolog. Specify a separate file for each job, otherwise
1184 the iologs will be interspersed and the file may be corrupt.
1186 read_iolog=str Open an iolog with the specified file name and replay the
1187 io patterns it contains. This can be used to store a
1188 workload and replay it sometime later. The iolog given
1189 may also be a blktrace binary file, which allows fio
1190 to replay a workload captured by blktrace. See blktrace
1191 for how to capture such logging data. For blktrace replay,
1192 the file needs to be turned into a blkparse binary data
1193 file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
1195 replay_no_stall=int When replaying I/O with read_iolog the default behavior
1196 is to attempt to respect the time stamps within the log and
1197 replay them with the appropriate delay between IOPS. By
1198 setting this variable fio will not respect the timestamps and
1199 attempt to replay them as fast as possible while still
1200 respecting ordering. The result is the same I/O pattern to a
1201 given device, but different timings.
1203 replay_redirect=str While replaying I/O patterns using read_iolog the
1204 default behavior is to replay the IOPS onto the major/minor
1205 device that each IOP was recorded from. This is sometimes
1206 undesireable because on a different machine those major/minor
1207 numbers can map to a different device. Changing hardware on
1208 the same system can also result in a different major/minor
1209 mapping. Replay_redirect causes all IOPS to be replayed onto
1210 the single specified device regardless of the device it was
1211 recorded from. i.e. replay_redirect=/dev/sdc would cause all
1212 IO in the blktrace to be replayed onto /dev/sdc. This means
1213 multiple devices will be replayed onto a single, if the trace
1214 contains multiple devices. If you want multiple devices to be
1215 replayed concurrently to multiple redirected devices you must
1216 blkparse your trace into separate traces and replay them with
1217 independent fio invocations. Unfortuantely this also breaks
1218 the strict time ordering between multiple device accesses.
1220 write_bw_log=str If given, write a bandwidth log of the jobs in this job
1221 file. Can be used to store data of the bandwidth of the
1222 jobs in their lifetime. The included fio_generate_plots
1223 script uses gnuplot to turn these text files into nice
1224 graphs. See write_lat_log for behaviour of given
1225 filename. For this option, the suffix is _bw.log.
1227 write_lat_log=str Same as write_bw_log, except that this option stores io
1228 submission, completion, and total latencies instead. If no
1229 filename is given with this option, the default filename of
1230 "jobname_type.log" is used. Even if the filename is given,
1231 fio will still append the type of log. So if one specifies
1235 The actual log names will be foo_slat.log, foo_clat.log,
1236 and foo_lat.log. This helps fio_generate_plot fine the logs
1239 write_bw_log=str If given, write an IOPS log of the jobs in this job
1240 file. See write_bw_log.
1242 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
1243 given with this option, the default filename of
1244 "jobname_type.log" is used. Even if the filename is given,
1245 fio will still append the type of log.
1247 log_avg_msec=int By default, fio will log an entry in the iops, latency,
1248 or bw log for every IO that completes. When writing to the
1249 disk log, that can quickly grow to a very large size. Setting
1250 this option makes fio average the each log entry over the
1251 specified period of time, reducing the resolution of the log.
1254 lockmem=int Pin down the specified amount of memory with mlock(2). Can
1255 potentially be used instead of removing memory or booting
1256 with less memory to simulate a smaller amount of memory.
1257 The amount specified is per worker.
1259 exec_prerun=str Before running this job, issue the command specified
1262 exec_postrun=str After the job completes, issue the command specified
1265 ioscheduler=str Attempt to switch the device hosting the file to the specified
1266 io scheduler before running.
1268 disk_util=bool Generate disk utilization statistics, if the platform
1269 supports it. Defaults to on.
1271 disable_lat=bool Disable measurements of total latency numbers. Useful
1272 only for cutting back the number of calls to gettimeofday,
1273 as that does impact performance at really high IOPS rates.
1274 Note that to really get rid of a large amount of these
1275 calls, this option must be used with disable_slat and
1278 disable_clat=bool Disable measurements of completion latency numbers. See
1281 disable_slat=bool Disable measurements of submission latency numbers. See
1284 disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
1287 clat_percentiles=bool Enable the reporting of percentiles of
1288 completion latencies.
1290 percentile_list=float_list Overwrite the default list of percentiles
1291 for completion latencies. Each number is a floating
1292 number in the range (0,100], and the maximum length of
1293 the list is 20. Use ':' to separate the numbers, and
1294 list the numbers in ascending order. For example,
1295 --percentile_list=99.5:99.9 will cause fio to report
1296 the values of completion latency below which 99.5% and
1297 99.9% of the observed latencies fell, respectively.
1299 clocksource=str Use the given clocksource as the base of timing. The
1300 supported options are:
1302 gettimeofday gettimeofday(2)
1304 clock_gettime clock_gettime(2)
1306 cpu Internal CPU clock source
1308 cpu is the preferred clocksource if it is reliable, as it
1309 is very fast (and fio is heavy on time calls). Fio will
1310 automatically use this clocksource if it's supported and
1311 considered reliable on the system it is running on, unless
1312 another clocksource is specifically set. For x86/x86-64 CPUs,
1313 this means supporting TSC Invariant.
1315 gtod_reduce=bool Enable all of the gettimeofday() reducing options
1316 (disable_clat, disable_slat, disable_bw) plus reduce
1317 precision of the timeout somewhat to really shrink
1318 the gettimeofday() call count. With this option enabled,
1319 we only do about 0.4% of the gtod() calls we would have
1320 done if all time keeping was enabled.
1322 gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of
1323 execution to just getting the current time. Fio (and
1324 databases, for instance) are very intensive on gettimeofday()
1325 calls. With this option, you can set one CPU aside for
1326 doing nothing but logging current time to a shared memory
1327 location. Then the other threads/processes that run IO
1328 workloads need only copy that segment, instead of entering
1329 the kernel with a gettimeofday() call. The CPU set aside
1330 for doing these time calls will be excluded from other
1331 uses. Fio will manually clear it from the CPU mask of other
1334 continue_on_error=str Normally fio will exit the job on the first observed
1335 failure. If this option is set, fio will continue the job when
1336 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
1337 is exceeded or the I/O size specified is completed. If this
1338 option is used, there are two more stats that are appended,
1339 the total error count and the first error. The error field
1340 given in the stats is the first error that was hit during the
1343 The allowed values are:
1345 none Exit on any IO or verify errors.
1347 read Continue on read errors, exit on all others.
1349 write Continue on write errors, exit on all others.
1351 io Continue on any IO error, exit on all others.
1353 verify Continue on verify errors, exit on all others.
1355 all Continue on all errors.
1357 0 Backward-compatible alias for 'none'.
1359 1 Backward-compatible alias for 'all'.
1361 ignore_error=str Sometimes you want to ignore some errors during test
1362 in that case you can specify error list for each error type.
1363 ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
1364 errors for given error type is separated with ':'. Error
1365 may be symbol ('ENOSPC', 'ENOMEM') or integer.
1367 ignore_error=EAGAIN,ENOSPC:122
1368 This option will ignore EAGAIN from READ, and ENOSPC and
1369 122(EDQUOT) from WRITE.
1371 error_dump=bool If set dump every error even if it is non fatal, true
1372 by default. If disabled only fatal error will be dumped
1374 cgroup=str Add job to this control group. If it doesn't exist, it will
1375 be created. The system must have a mounted cgroup blkio
1376 mount point for this to work. If your system doesn't have it
1377 mounted, you can do so with:
1379 # mount -t cgroup -o blkio none /cgroup
1381 cgroup_weight=int Set the weight of the cgroup to this value. See
1382 the documentation that comes with the kernel, allowed values
1383 are in the range of 100..1000.
1385 cgroup_nodelete=bool Normally fio will delete the cgroups it has created after
1386 the job completion. To override this behavior and to leave
1387 cgroups around after the job completion, set cgroup_nodelete=1.
1388 This can be useful if one wants to inspect various cgroup
1389 files after job completion. Default: false
1391 uid=int Instead of running as the invoking user, set the user ID to
1392 this value before the thread/process does any work.
1394 gid=int Set group ID, see uid.
1396 flow_id=int The ID of the flow. If not specified, it defaults to being a
1397 global flow. See flow.
1399 flow=int Weight in token-based flow control. If this value is used, then
1400 there is a 'flow counter' which is used to regulate the
1401 proportion of activity between two or more jobs. fio attempts
1402 to keep this flow counter near zero. The 'flow' parameter
1403 stands for how much should be added or subtracted to the flow
1404 counter on each iteration of the main I/O loop. That is, if
1405 one job has flow=8 and another job has flow=-1, then there
1406 will be a roughly 1:8 ratio in how much one runs vs the other.
1408 flow_watermark=int The maximum value that the absolute value of the flow
1409 counter is allowed to reach before the job must wait for a
1410 lower value of the counter.
1412 flow_sleep=int The period of time, in microseconds, to wait after the flow
1413 watermark has been exceeded before retrying operations
1415 In addition, there are some parameters which are only valid when a specific
1416 ioengine is in use. These are used identically to normal parameters, with the
1417 caveat that when used on the command line, they must come after the ioengine
1418 that defines them is selected.
1420 [libaio] userspace_reap Normally, with the libaio engine in use, fio will use
1421 the io_getevents system call to reap newly returned events.
1422 With this flag turned on, the AIO ring will be read directly
1423 from user-space to reap events. The reaping mode is only
1424 enabled when polling for a minimum of 0 events (eg when
1425 iodepth_batch_complete=0).
1427 [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles.
1429 [cpu] cpuchunks=int Split the load into cycles of the given time. In
1432 [netsplice] hostname=str
1433 [net] hostname=str The host name or IP address to use for TCP or UDP based IO.
1434 If the job is a TCP listener or UDP reader, the hostname is not
1435 used and must be omitted.
1437 [netsplice] port=int
1438 [net] port=int The TCP or UDP port to bind to or connect to.
1440 [netsplice] nodelay=bool
1441 [net] nodelay=bool Set TCP_NODELAY on TCP connections.
1443 [netsplice] protocol=str
1444 [netsplice] proto=str
1446 [net] proto=str The network protocol to use. Accepted values are:
1448 tcp Transmission control protocol
1449 udp User datagram protocol
1450 unix UNIX domain socket
1452 When the protocol is TCP or UDP, the port must also be given,
1453 as well as the hostname if the job is a TCP listener or UDP
1454 reader. For unix sockets, the normal filename option should be
1455 used and the port is invalid.
1457 [net] listen For TCP network connections, tell fio to listen for incoming
1458 connections rather than initiating an outgoing connection. The
1459 hostname must be omitted if this option is used.
1460 [net] pingpong Normal a network writer will just continue writing data, and
1461 a network reader will just consume packages. If pingpong=1
1462 is set, a writer will send its normal payload to the reader,
1463 then wait for the reader to send the same payload back. This
1464 allows fio to measure network latencies. The submission
1465 and completion latencies then measure local time spent
1466 sending or receiving, and the completion latency measures
1467 how long it took for the other end to receive and send back.
1469 [e4defrag] donorname=str
1470 File will be used as a block donor(swap extents between files)
1471 [e4defrag] inplace=int
1472 Configure donor file blocks allocation strategy
1473 0(default): Preallocate donor's file on init
1474 1 : allocate space immidietly inside defragment event,
1475 and free right after event
1479 6.0 Interpreting the output
1480 ---------------------------
1482 fio spits out a lot of output. While running, fio will display the
1483 status of the jobs created. An example of that would be:
1485 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
1487 The characters inside the square brackets denote the current status of
1488 each thread. The possible values (in typical life cycle order) are:
1492 P Thread setup, but not started.
1494 I Thread initialized, waiting or generating necessary data.
1495 p Thread running pre-reading file(s).
1496 R Running, doing sequential reads.
1497 r Running, doing random reads.
1498 W Running, doing sequential writes.
1499 w Running, doing random writes.
1500 M Running, doing mixed sequential reads/writes.
1501 m Running, doing mixed random reads/writes.
1502 F Running, currently waiting for fsync()
1503 V Running, doing verification of written data.
1504 E Thread exited, not reaped by main thread yet.
1506 X Thread reaped, exited with an error.
1507 K Thread reaped, exited due to signal.
1509 The other values are fairly self explanatory - number of threads
1510 currently running and doing io, rate of io since last check (read speed
1511 listed first, then write speed), and the estimated completion percentage
1512 and time for the running group. It's impossible to estimate runtime of
1513 the following groups (if any). Note that the string is displayed in order,
1514 so it's possible to tell which of the jobs are currently doing what. The
1515 first character is the first job defined in the job file, and so forth.
1517 When fio is done (or interrupted by ctrl-c), it will show the data for
1518 each thread, group of threads, and disks in that order. For each data
1519 direction, the output looks like:
1521 Client1 (g=0): err= 0:
1522 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
1523 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
1524 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
1525 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
1526 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
1527 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
1528 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1529 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1530 issued r/w: total=0/32768, short=0/0
1531 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
1532 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
1534 The client number is printed, along with the group id and error of that
1535 thread. Below is the io statistics, here for writes. In the order listed,
1538 io= Number of megabytes io performed
1539 bw= Average bandwidth rate
1540 iops= Average IOs performed per second
1541 runt= The runtime of that thread
1542 slat= Submission latency (avg being the average, stdev being the
1543 standard deviation). This is the time it took to submit
1544 the io. For sync io, the slat is really the completion
1545 latency, since queue/complete is one operation there. This
1546 value can be in milliseconds or microseconds, fio will choose
1547 the most appropriate base and print that. In the example
1548 above, milliseconds is the best scale. Note: in --minimal mode
1549 latencies are always expressed in microseconds.
1550 clat= Completion latency. Same names as slat, this denotes the
1551 time from submission to completion of the io pieces. For
1552 sync io, clat will usually be equal (or very close) to 0,
1553 as the time from submit to complete is basically just
1554 CPU time (io has already been done, see slat explanation).
1555 bw= Bandwidth. Same names as the xlat stats, but also includes
1556 an approximate percentage of total aggregate bandwidth
1557 this thread received in this group. This last value is
1558 only really useful if the threads in this group are on the
1559 same disk, since they are then competing for disk access.
1560 cpu= CPU usage. User and system time, along with the number
1561 of context switches this thread went through, usage of
1562 system and user time, and finally the number of major
1563 and minor page faults.
1564 IO depths= The distribution of io depths over the job life time. The
1565 numbers are divided into powers of 2, so for example the
1566 16= entries includes depths up to that value but higher
1567 than the previous entry. In other words, it covers the
1568 range from 16 to 31.
1569 IO submit= How many pieces of IO were submitting in a single submit
1570 call. Each entry denotes that amount and below, until
1571 the previous entry - eg, 8=100% mean that we submitted
1572 anywhere in between 5-8 ios per submit call.
1573 IO complete= Like the above submit number, but for completions instead.
1574 IO issued= The number of read/write requests issued, and how many
1576 IO latencies= The distribution of IO completion latencies. This is the
1577 time from when IO leaves fio and when it gets completed.
1578 The numbers follow the same pattern as the IO depths,
1579 meaning that 2=1.6% means that 1.6% of the IO completed
1580 within 2 msecs, 20=12.8% means that 12.8% of the IO
1581 took more than 10 msecs, but less than (or equal to) 20 msecs.
1583 After each client has been listed, the group statistics are printed. They
1584 will look like this:
1586 Run status group 0 (all jobs):
1587 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
1588 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
1590 For each data direction, it prints:
1592 io= Number of megabytes io performed.
1593 aggrb= Aggregate bandwidth of threads in this group.
1594 minb= The minimum average bandwidth a thread saw.
1595 maxb= The maximum average bandwidth a thread saw.
1596 mint= The smallest runtime of the threads in that group.
1597 maxt= The longest runtime of the threads in that group.
1599 And finally, the disk statistics are printed. They will look like this:
1601 Disk stats (read/write):
1602 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
1604 Each value is printed for both reads and writes, with reads first. The
1607 ios= Number of ios performed by all groups.
1608 merge= Number of merges io the io scheduler.
1609 ticks= Number of ticks we kept the disk busy.
1610 io_queue= Total time spent in the disk queue.
1611 util= The disk utilization. A value of 100% means we kept the disk
1612 busy constantly, 50% would be a disk idling half of the time.
1614 It is also possible to get fio to dump the current output while it is
1615 running, without terminating the job. To do that, send fio the USR1 signal.
1616 You can also get regularly timed dumps by using the --status-interval
1617 parameter, or by creating a file in /tmp named fio-dump-status. If fio
1618 sees this file, it will unlink it and dump the current output status.
1624 For scripted usage where you typically want to generate tables or graphs
1625 of the results, fio can output the results in a semicolon separated format.
1626 The format is one long line of values, such as:
1628 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%
1629 A description of this job goes here.
1631 The job description (if provided) follows on a second line.
1633 To enable terse output, use the --minimal command line option. The first
1634 value is the version of the terse output format. If the output has to
1635 be changed for some reason, this number will be incremented by 1 to
1636 signify that change.
1638 Split up, the format is as follows:
1640 terse version, fio version, jobname, groupid, error
1642 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
1643 Submission latency: min, max, mean, deviation (usec)
1644 Completion latency: min, max, mean, deviation (usec)
1645 Completion latency percentiles: 20 fields (see below)
1646 Total latency: min, max, mean, deviation (usec)
1647 Bw (KB/s): min, max, aggregate percentage of total, mean, deviation
1649 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
1650 Submission latency: min, max, mean, deviation (usec)
1651 Completion latency: min, max, mean, deviation (usec)
1652 Completion latency percentiles: 20 fields (see below)
1653 Total latency: min, max, mean, deviation (usec)
1654 Bw (KB/s): min, max, aggregate percentage of total, mean, deviation
1655 CPU usage: user, system, context switches, major faults, minor faults
1656 IO depths: <=1, 2, 4, 8, 16, 32, >=64
1657 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
1658 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
1659 Disk utilization: Disk name, Read ios, write ios,
1660 Read merges, write merges,
1661 Read ticks, write ticks,
1662 Time spent in queue, disk utilization percentage
1663 Additional Info (dependant on continue_on_error, default off): total # errors, first error code
1665 Additional Info (dependant on description being set): Text description
1667 Completion latency percentiles can be a grouping of up to 20 sets, so
1668 for the terse output fio writes all of them. Each field will look like this:
1672 which is the Xth percentile, and the usec latency associated with it.
1674 For disk utilization, all disks used by fio are shown. So for each disk
1675 there will be a disk utilization section.
1678 8.0 Trace file format
1679 ---------------------
1680 There are two trace file format that you can encounter. The older (v1) format
1681 is unsupported since version 1.20-rc3 (March 2008). It will still be described
1682 below in case that you get an old trace and want to understand it.
1684 In any case the trace is a simple text file with a single action per line.
1687 8.1 Trace file format v1
1688 ------------------------
1689 Each line represents a single io action in the following format:
1693 where rw=0/1 for read/write, and the offset and length entries being in bytes.
1695 This format is not supported in Fio versions => 1.20-rc3.
1698 8.2 Trace file format v2
1699 ------------------------
1700 The second version of the trace file format was added in Fio version 1.17.
1701 It allows to access more then one file per trace and has a bigger set of
1702 possible file actions.
1704 The first line of the trace file has to be:
1708 Following this can be lines in two different formats, which are described below.
1710 The file management format:
1714 The filename is given as an absolute path. The action can be one of these:
1716 add Add the given filename to the trace
1717 open Open the file with the given filename. The filename has to have
1718 been added with the add action before.
1719 close Close the file with the given filename. The file has to have been
1723 The file io action format:
1725 filename action offset length
1727 The filename is given as an absolute path, and has to have been added and opened
1728 before it can be used with this format. The offset and length are given in
1729 bytes. The action can be one of these:
1731 wait Wait for 'offset' microseconds. Everything below 100 is discarded.
1732 read Read 'length' bytes beginning from 'offset'
1733 write Write 'length' bytes beginning from 'offset'
1734 sync fsync() the file
1735 datasync fdatasync() the file
1736 trim trim the given file from the given 'offset' for 'length' bytes
1739 9.0 CPU idleness profiling
1740 --------------------------
1741 In some cases, we want to understand CPU overhead in a test. For example,
1742 we test patches for the specific goodness of whether they reduce CPU usage.
1743 fio implements a balloon approach to create a thread per CPU that runs at
1744 idle priority, meaning that it only runs when nobody else needs the cpu.
1745 By measuring the amount of work completed by the thread, idleness of each
1746 CPU can be derived accordingly.
1748 An unit work is defined as touching a full page of unsigned characters. Mean
1749 and standard deviation of time to complete an unit work is reported in "unit
1750 work" section. Options can be chosen to report detailed percpu idleness or
1751 overall system idleness by aggregating percpu stats.
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