1 .TH fio 1 "September 2007" "User Manual"
3 fio \- flexible I/O tester
6 [\fIoptions\fR] [\fIjobfile\fR]...
9 is a tool that will spawn a number of threads or processes doing a
10 particular type of I/O action as specified by the user.
11 The typical use of fio is to write a job file matching the I/O load
12 one wants to simulate.
15 .BI \-\-output \fR=\fPfilename
16 Write output to \fIfilename\fR.
18 .BI \-\-timeout \fR=\fPtimeout
19 Limit run time to \fItimeout\fR seconds.
22 Generate per-job latency logs.
25 Generate per-job bandwidth logs.
28 Print statistics in a terse, semicolon-delimited format.
30 .BI \-\-showcmd \fR=\fPjobfile
31 Convert \fIjobfile\fR to a set of command-line options.
34 Enable read-only safety checks.
36 .BI \-\-eta \fR=\fPwhen
37 Specifies when real-time ETA estimate should be printed. \fIwhen\fR may
38 be one of `always', `never' or `auto'.
40 .BI \-\-section \fR=\fPsec
41 Only run section \fIsec\fR from job file.
43 .BI \-\-cmdhelp \fR=\fPcommand
44 Print help information for \fIcommand\fR. May be `all' for all commands.
46 .BI \-\-debug \fR=\fPtype
47 Enable verbose tracing of various fio actions. May be `all' for all types
48 or individual types seperated by a comma (eg --debug=io,file). `help' will
49 list all available tracing options.
52 Display usage information and exit.
55 Display version information and exit.
57 Job files are in `ini' format. They consist of one or more
58 job definitions, which begin with a job name in square brackets and
59 extend to the next job name. The job name can be any ASCII string
60 except `global', which has a special meaning. Following the job name is
61 a sequence of zero or more parameters, one per line, that define the
62 behavior of the job. Any line starting with a `;' or `#' character is
63 considered a comment and ignored.
65 If \fIjobfile\fR is specified as `-', the job file will be read from
68 The global section contains default parameters for jobs specified in the
69 job file. A job is only affected by global sections residing above it,
70 and there may be any number of global sections. Specific job definitions
71 may override any parameter set in global sections.
74 Some parameters may take arguments of a specific type. The types used are:
77 String: a sequence of alphanumeric characters.
80 SI integer: a whole number, possibly containing a suffix denoting the base unit
81 of the value. Accepted suffixes are `k', 'M' and 'G', denoting kilo (1024),
82 mega (1024*1024) and giga (1024*1024*1024) respectively. If prefixed with '0x',
83 the value is assumed to be base 16 (hexadecimal).
86 Boolean: a true or false value. `0' denotes false, `1' denotes true.
89 Integer range: a range of integers specified in the format
90 \fIlower\fR:\fIupper\fR or \fIlower\fR\-\fIupper\fR. \fIlower\fR and
91 \fIupper\fR may contain a suffix as described above. If an option allows two
92 sets of ranges, they are separated with a `,' or `/' character. For example:
97 May be used to override the job name. On the command line, this parameter
98 has the special purpose of signalling the start of a new job.
100 .BI description \fR=\fPstr
101 Human-readable description of the job. It is printed when the job is run, but
102 otherwise has no special purpose.
104 .BI directory \fR=\fPstr
105 Prefix filenames with this directory. Used to place files in a location other
108 .BI filename \fR=\fPstr
110 normally makes up a file name based on the job name, thread number, and file
111 number. If you want to share files between threads in a job or several jobs,
112 specify a \fIfilename\fR for each of them to override the default. If the I/O
113 engine used is `net', \fIfilename\fR is the host and port to connect to in the
114 format \fIhost\fR/\fIport\fR. If the I/O engine is file-based, you can specify
115 a number of files by separating the names with a `:' character. `\-' is a
116 reserved name, meaning stdin or stdout, depending on the read/write direction
119 .BI opendir \fR=\fPstr
120 Recursively open any files below directory \fIstr\fR.
122 .BI readwrite \fR=\fPstr "\fR,\fP rw" \fR=\fPstr
123 Type of I/O pattern. Accepted values are:
140 Mixed sequential reads and writes.
143 Mixed random reads and writes.
146 For mixed I/O, the default split is 50/50. For random I/O, the number of I/Os
147 to perform before getting a new offset can be specified by appending
148 `:\fIint\fR' to the pattern type. The default is 1.
151 .BI randrepeat \fR=\fPbool
152 Seed the random number generator in a predictable way so results are repeatable
153 across runs. Default: true.
155 .BI fadvise_hint \fR=\fPbool
156 Disable use of \fIposix_fadvise\fR\|(2) to advise the kernel what I/O patterns
157 are likely to be issued. Default: true.
160 Total size of I/O for this job. \fBfio\fR will run until this many bytes have
161 been transfered, unless limited by other options (\fBruntime\fR, for instance).
162 Unless \fBnr_files\fR and \fBfilesize\fR options are given, this amount will be
163 divided between the available files for the job.
165 .BI filesize \fR=\fPirange
166 Individual file sizes. May be a range, in which case \fBfio\fR will select sizes
167 for files at random within the given range, limited to \fBsize\fR in total (if
168 that is given). If \fBfilesize\fR is not specified, each created file is the
171 .BI blocksize \fR=\fPint[,int] "\fR,\fB bs" \fR=\fPint[,int]
172 Block size for I/O units. Default: 4k. Values for reads and writes can be
173 specified seperately in the format \fIread\fR,\fIwrite\fR, either of
174 which may be empty to leave that value at its default.
176 .BI blocksize_range \fR=\fPirange[,irange] "\fR,\fB bsrange" \fR=\fPirange[,irange]
177 Specify a range of I/O block sizes. The issued I/O unit will always be a
178 multiple of the minimum size, unless \fBblocksize_unaligned\fR is set. Applies
179 to both reads and writes if only one range is given, but can be specified
180 seperately with a comma seperating the values. Example: bsrange=1k-4k,2k-8k.
181 Also (see \fBblocksize\fR).
183 .BI bssplit \fR=\fPstr
184 This option allows even finer grained control of the block sizes issued,
185 not just even splits between them. With this option, you can weight various
186 block sizes for exact control of the issued IO for a job that has mixed
187 block sizes. The format of the option is bssplit=blocksize/percentage,
188 optionally adding as many definitions as needed seperated by a colon.
189 Example: bssplit=4k/10:64k/50:32k/40 would issue 50% 64k blocks, 10% 4k
190 blocks and 40% 32k blocks.
192 .B blocksize_unaligned\fR,\fP bs_unaligned
193 If set, any size in \fBblocksize_range\fR may be used. This typically won't
194 work with direct I/O, as that normally requires sector alignment.
196 .BI blockalign \fR=\fPint[,int] "\fR,\fB ba" \fR=\fPint[,int]
197 At what boundary to align random IO offsets. Defaults to the same as
198 'blocksize' the minimum blocksize given. Minimum alignment is typically 512b
199 for using direct IO, though it usually depends on the hardware block size.
200 This option is mutually exclusive with using a random map for files, so it
201 will turn off that option.
204 Initialise buffers with all zeros. Default: fill buffers with random data.
206 .BI nrfiles \fR=\fPint
207 Number of files to use for this job. Default: 1.
209 .BI openfiles \fR=\fPint
210 Number of files to keep open at the same time. Default: \fBnrfiles\fR.
212 .BI file_service_type \fR=\fPstr
213 Defines how files to service are selected. The following types are defined:
218 Choose a file at random
221 Round robin over open files (default).
223 Do each file in the set sequentially.
226 The number of I/Os to issue before switching a new file can be specified by
227 appending `:\fIint\fR' to the service type.
230 .BI ioengine \fR=\fPstr
231 Defines how the job issues I/O. The following types are defined:
236 Basic \fIread\fR\|(2) or \fIwrite\fR\|(2) I/O. \fIfseek\fR\|(2) is used to
237 position the I/O location.
240 Basic \fIpread\fR\|(2) or \fIpwrite\fR\|(2) I/O.
243 Basic \fIreadv\fR\|(2) or \fIwritev\fR\|(2) I/O. Will emulate queuing by
244 coalescing adjacents IOs into a single submission.
247 Linux native asynchronous I/O.
250 glibc POSIX asynchronous I/O using \fIaio_read\fR\|(3) and \fIaio_write\fR\|(3).
253 File is memory mapped with \fImmap\fR\|(2) and data copied using
257 \fIsplice\fR\|(2) is used to transfer the data and \fIvmsplice\fR\|(2) to
258 transfer data from user-space to the kernel.
261 Use the syslet system calls to make regular read/write asynchronous.
264 SCSI generic sg v3 I/O. May be either synchronous using the SG_IO ioctl, or if
265 the target is an sg character device, we use \fIread\fR\|(2) and
266 \fIwrite\fR\|(2) for asynchronous I/O.
269 Doesn't transfer any data, just pretends to. Mainly used to exercise \fBfio\fR
270 itself and for debugging and testing purposes.
273 Transfer over the network. \fBfilename\fR must be set appropriately to
274 `\fIhost\fR/\fIport\fR' regardless of data direction. If receiving, only the
275 \fIport\fR argument is used.
278 Like \fBnet\fR, but uses \fIsplice\fR\|(2) and \fIvmsplice\fR\|(2) to map data
282 Doesn't transfer any data, but burns CPU cycles according to \fBcpuload\fR and
283 \fBcpucycles\fR parameters.
286 The GUASI I/O engine is the Generic Userspace Asynchronous Syscall Interface
287 approach to asycnronous I/O.
289 See <http://www.xmailserver.org/guasi\-lib.html>.
292 Loads an external I/O engine object file. Append the engine filename as
297 .BI iodepth \fR=\fPint
298 Number of I/O units to keep in flight against the file. Default: 1.
300 .BI iodepth_batch \fR=\fPint
301 Number of I/Os to submit at once. Default: \fBiodepth\fR.
303 .BI iodepth_low \fR=\fPint
304 Low watermark indicating when to start filling the queue again. Default:
307 .BI direct \fR=\fPbool
308 If true, use non-buffered I/O (usually O_DIRECT). Default: false.
310 .BI buffered \fR=\fPbool
311 If true, use buffered I/O. This is the opposite of the \fBdirect\fR parameter.
314 .BI offset \fR=\fPint
315 Offset in the file to start I/O. Data before the offset will not be touched.
318 How many I/Os to perform before issuing an \fBfsync\fR\|(2) of dirty data. If
319 0, don't sync. Default: 0.
321 .BI overwrite \fR=\fPbool
322 If writing, setup the file first and do overwrites. Default: false.
324 .BI end_fsync \fR=\fPbool
325 Sync file contents when job exits. Default: false.
327 .BI fsync_on_close \fR=\fPbool
328 If true, sync file contents on close. This differs from \fBend_fsync\fR in that
329 it will happen on every close, not just at the end of the job. Default: false.
331 .BI rwmixcycle \fR=\fPint
332 How many milliseconds before switching between reads and writes for a mixed
333 workload. Default: 500ms.
335 .BI rwmixread \fR=\fPint
336 Percentage of a mixed workload that should be reads. Default: 50.
338 .BI rwmixwrite \fR=\fPint
339 Percentage of a mixed workload that should be writes. If \fBrwmixread\fR and
340 \fBwrmixwrite\fR are given and do not sum to 100%, the latter of the two
341 overrides the first. Default: 50.
344 Normally \fBfio\fR will cover every block of the file when doing random I/O. If
345 this parameter is given, a new offset will be chosen without looking at past
346 I/O history. This parameter is mutually exclusive with \fBverify\fR.
349 Run job with given nice value. See \fInice\fR\|(2).
352 Set I/O priority value of this job between 0 (highest) and 7 (lowest). See
355 .BI prioclass \fR=\fPint
356 Set I/O priority class. See \fIionice\fR\|(1).
358 .BI thinktime \fR=\fPint
359 Stall job for given number of microseconds between issuing I/Os.
361 .BI thinktime_spin \fR=\fPint
362 Pretend to spend CPU time for given number of microseconds, sleeping the rest
363 of the time specified by \fBthinktime\fR. Only valid if \fBthinktime\fR is set.
365 .BI thinktime_blocks \fR=\fPint
366 Number of blocks to issue before waiting \fBthinktime\fR microseconds.
370 Cap bandwidth used by this job to this number of KiB/s.
372 .BI ratemin \fR=\fPint
373 Tell \fBfio\fR to do whatever it can to maintain at least the given bandwidth.
374 Failing to meet this requirement will cause the job to exit.
376 .BI rate_iops \fR=\fPint
377 Cap the bandwidth to this number of IOPS. If \fBblocksize\fR is a range, the
378 smallest block size is used as the metric.
380 .BI rate_iops_min \fR=\fPint
381 If this rate of I/O is not met, the job will exit.
383 .BI ratecycle \fR=\fPint
384 Average bandwidth for \fBrate\fR and \fBratemin\fR over this number of
385 milliseconds. Default: 1000ms.
387 .BI cpumask \fR=\fPint
388 Set CPU affinity for this job. \fIint\fR is a bitmask of allowed CPUs the job
389 may run on. See \fBsched_setaffinity\fR\|(2).
391 .BI cpus_allowed \fR=\fPstr
392 Same as \fBcpumask\fR, but allows a comma-delimited list of CPU numbers.
394 .BI startdelay \fR=\fPint
395 Delay start of job for the specified number of seconds.
397 .BI runtime \fR=\fPint
398 Terminate processing after the specified number of seconds.
401 If given, run for the specified \fBruntime\fR duration even if the files are
402 completely read or written. The same workload will be repeated as many times
403 as \fBruntime\fR allows.
405 .BI invalidate \fR=\fPbool
406 Invalidate buffer-cache for the file prior to starting I/O. Default: true.
409 Use synchronous I/O for buffered writes. For the majority of I/O engines,
410 this means using O_SYNC. Default: false.
412 .BI iomem \fR=\fPstr "\fR,\fP mem" \fR=\fPstr
413 Allocation method for I/O unit buffer. Allowed values are:
418 Allocate memory with \fImalloc\fR\|(3).
421 Use shared memory buffers allocated through \fIshmget\fR\|(2).
424 Same as \fBshm\fR, but use huge pages as backing.
427 Use \fImmap\fR\|(2) for allocation. Uses anonymous memory unless a filename
428 is given after the option in the format `:\fIfile\fR'.
431 Same as \fBmmap\fR, but use huge files as backing.
434 The amount of memory allocated is the maximum allowed \fBblocksize\fR for the
435 job multiplied by \fBiodepth\fR. For \fBshmhuge\fR or \fBmmaphuge\fR to work,
436 the system must have free huge pages allocated. \fBmmaphuge\fR also needs to
437 have hugetlbfs mounted, and \fIfile\fR must point there.
440 .BI hugepage\-size \fR=\fPint
441 Defines the size of a huge page. Must be at least equal to the system setting.
442 Should be a multiple of 1MiB. Default: 4MiB.
445 Terminate all jobs when one finishes. Default: wait for each job to finish.
447 .BI bwavgtime \fR=\fPint
448 Average bandwidth calculations over the given time in milliseconds. Default:
451 .BI create_serialize \fR=\fPbool
452 If true, serialize file creation for the jobs. Default: true.
454 .BI create_fsync \fR=\fPbool
455 \fIfsync\fR\|(2) data file after creation. Default: true.
457 .BI create_on_open \fR=\fPbool
458 If true, the files are not created until they are opened for IO by the job.
460 .BI unlink \fR=\fPbool
461 Unlink job files when done. Default: false.
464 Specifies the number of iterations (runs of the same workload) of this job.
467 .BI do_verify \fR=\fPbool
468 Run the verify phase after a write phase. Only valid if \fBverify\fR is set.
471 .BI verify \fR=\fPstr
472 Method of verifying file contents after each iteration of the job. Allowed
477 .B md5 crc16 crc32 crc64 crc7 sha256 sha512
478 Store appropriate checksum in the header of each block.
481 Write extra information about each I/O (timestamp, block number, etc.). The
482 block number is verified.
485 Fill I/O buffers with a specific pattern that is used to verify. The pattern is
486 specified by appending `:\fIint\fR' to the parameter. \fIint\fR cannot be larger
490 Pretend to verify. Used for testing internals.
494 .BI verify_sort \fR=\fPbool
495 If true, written verify blocks are sorted if \fBfio\fR deems it to be faster to
496 read them back in a sorted manner. Default: true.
498 .BI verify_offset \fR=\fPint
499 Swap the verification header with data somewhere else in the block before
500 writing. It is swapped back before verifying.
502 .BI verify_interval \fR=\fPint
503 Write the verification header for this number of bytes, which should divide
504 \fBblocksize\fR. Default: \fBblocksize\fR.
506 .BI verify_fatal \fR=\fPbool
507 If true, exit the job on the first observed verification failure. Default:
511 Wait for preceeding jobs in the job file to exit before starting this one.
512 \fBstonewall\fR implies \fBnew_group\fR.
515 Start a new reporting group. If not given, all jobs in a file will be part
516 of the same reporting group, unless separated by a stonewall.
518 .BI numjobs \fR=\fPint
519 Number of clones (processes/threads performing the same workload) of this job.
523 If set, display per-group reports instead of per-job when \fBnumjobs\fR is
527 Use threads created with \fBpthread_create\fR\|(3) instead of processes created
528 with \fBfork\fR\|(2).
530 .BI zonesize \fR=\fPint
531 Divide file into zones of the specified size in bytes. See \fBzoneskip\fR.
533 .BI zoneskip \fR=\fPint
534 Skip the specified number of bytes when \fBzonesize\fR bytes of data have been
537 .BI write_iolog \fR=\fPstr
538 Write the issued I/O patterns to the specified file.
540 .BI read_iolog \fR=\fPstr
541 Replay the I/O patterns contained in the specified file generated by
542 \fBwrite_iolog\fR, or may be a \fBblktrace\fR binary file.
545 If given, write bandwidth logs of the jobs in this file.
548 Same as \fBwrite_bw_log\fR, but writes I/O completion latencies.
550 .BI lockmem \fR=\fPint
551 Pin the specified amount of memory with \fBmlock\fR\|(2). Can be used to
552 simulate a smaller amount of memory.
554 .BI exec_prerun \fR=\fPstr
555 Before running the job, execute the specified command with \fBsystem\fR\|(3).
557 .BI exec_postrun \fR=\fPstr
558 Same as \fBexec_prerun\fR, but the command is executed after the job completes.
560 .BI ioscheduler \fR=\fPstr
561 Attempt to switch the device hosting the file to the specified I/O scheduler.
563 .BI cpuload \fR=\fPint
564 If the job is a CPU cycle-eater, attempt to use the specified percentage of
567 .BI cpuchunks \fR=\fPint
568 If the job is a CPU cycle-eater, split the load into cycles of the
569 given time in milliseconds.
571 .BI disk_util \fR=\fPbool
572 Generate disk utilization statistics if the platform supports it. Default: true.
574 While running, \fBfio\fR will display the status of the created jobs. For
578 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
581 The characters in the first set of brackets denote the current status of each
582 threads. The possible values are:
588 Setup but not started.
594 Initialized, waiting.
597 Running, doing sequential reads.
600 Running, doing random reads.
603 Running, doing sequential writes.
606 Running, doing random writes.
609 Running, doing mixed sequential reads/writes.
612 Running, doing mixed random reads/writes.
615 Running, currently waiting for \fBfsync\fR\|(2).
618 Running, verifying written data.
621 Exited, not reaped by main thread.
624 Exited, thread reaped.
628 The second set of brackets shows the estimated completion percentage of
629 the current group. The third set shows the read and write I/O rate,
630 respectively. Finally, the estimated run time of the job is displayed.
632 When \fBfio\fR completes (or is interrupted by Ctrl-C), it will show data
633 for each thread, each group of threads, and each disk, in that order.
635 Per-thread statistics first show the threads client number, group-id, and
636 error code. The remaining figures are as follows:
640 Number of megabytes of I/O performed.
643 Average data rate (bandwidth).
649 Submission latency minimum, maximum, average and standard deviation. This is
650 the time it took to submit the I/O.
653 Completion latency minimum, maximum, average and standard deviation. This
654 is the time between submission and completion.
657 Bandwidth minimum, maximum, percentage of aggregate bandwidth received, average
658 and standard deviation.
661 CPU usage statistics. Includes user and system time, number of context switches
662 this thread went through and number of major and minor page faults.
665 Distribution of I/O depths. Each depth includes everything less than (or equal)
666 to it, but greater than the previous depth.
669 Number of read/write requests issued, and number of short read/write requests.
672 Distribution of I/O completion latencies. The numbers follow the same pattern
676 The group statistics show:
681 Number of megabytes I/O performed.
684 Aggregate bandwidth of threads in the group.
687 Minimum average bandwidth a thread saw.
690 Maximum average bandwidth a thread saw.
693 Shortest runtime of threads in the group.
696 Longest runtime of threads in the group.
700 Finally, disk statistics are printed with reads first:
705 Number of I/Os performed by all groups.
708 Number of merges in the I/O scheduler.
711 Number of ticks we kept the disk busy.
714 Total time spent in the disk queue.
721 If the \fB\-\-minimal\fR option is given, the results will be printed in a
722 semicolon-delimited format suitable for scripted use. The fields are:
725 .B jobname, groupid, error
729 .B KiB I/O, bandwidth \fR(KiB/s)\fP, runtime \fR(ms)\fP
733 .B min, max, mean, standard deviation
737 .B min, max, mean, standard deviation
741 .B min, max, aggregate percentage of total, mean, standard deviation
747 .B KiB I/O, bandwidth \fR(KiB/s)\fP, runtime \fR(ms)\fP
751 .B min, max, mean, standard deviation
755 .B min, max, mean, standard deviation
759 .B min, max, aggregate percentage of total, mean, standard deviation
765 .B user, system, context switches, major page faults, minor page faults
768 IO depth distribution:
770 .B <=1, 2, 4, 8, 16, 32, >=64
773 IO latency distribution (ms):
775 .B <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000
782 was written by Jens Axboe <jens.axboe@oracle.com>.
784 This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au> based
785 on documentation by Jens Axboe.
787 Report bugs to the \fBfio\fR mailing list <fio-devel@kernel.dk>.
790 For further documentation see \fBHOWTO\fR and \fBREADME\fR.
792 Sample jobfiles are available in the \fBexamples\fR directory.
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