.TH fio 1 "September 2007" "User Manual"

.SH NAME

fio \- flexible I/O tester

.SH SYNOPSIS

.B fio

[\fIoptions\fR] [\fIjobfile\fR]...

.SH DESCRIPTION

.B fio

is a tool that will spawn a number of threads or processes doing a

particular type of I/O action as specified by the user.

The typical use of fio is to write a job file matching the I/O load

one wants to simulate.

.SH OPTIONS

.TP

.BI \-\-output \fR=\fPfilename

Write output to \fIfilename\fR.

.TP

.BI \-\-timeout \fR=\fPtimeout

Limit run time to \fItimeout\fR seconds.

.TP

.B \-\-latency\-log

Generate per-job latency logs.

.TP

.B \-\-bandwidth\-log

Generate per-job bandwidth logs.

.TP

.B \-\-minimal

Print statistics in a terse, semicolon-delimited format.

.TP

.BI \-\-showcmd \fR=\fPjobfile

Convert \fIjobfile\fR to a set of command-line options.

.TP

.B \-\-readonly

Enable read-only safety checks.

.TP

.BI \-\-eta \fR=\fPwhen

Specifies when real-time ETA estimate should be printed. \fIwhen\fR may

be one of `always', `never' or `auto'.

.TP

.BI \-\-section \fR=\fPsec

Only run section \fIsec\fR from job file.

.TP

.BI \-\-cmdhelp \fR=\fPcommand

Print help information for \fIcommand\fR. May be `all' for all commands.

.TP

.BI \-\-debug \fR=\fPtype

Enable verbose tracing of various fio actions. May be `all' for all types

or individual types seperated by a comma (eg \-\-debug=io,file). `help' will

list all available tracing options.

.TP

.B \-\-help

Display usage information and exit.

.TP

.B \-\-version

Display version information and exit.

.SH "JOB FILE FORMAT"

Job files are in `ini' format. They consist of one or more

job definitions, which begin with a job name in square brackets and

extend to the next job name. The job name can be any ASCII string

except `global', which has a special meaning. Following the job name is

a sequence of zero or more parameters, one per line, that define the

behavior of the job. Any line starting with a `;' or `#' character is

considered a comment and ignored.

.P

If \fIjobfile\fR is specified as `-', the job file will be read from

standard input.

.SS "Global Section"

The global section contains default parameters for jobs specified in the

job file. A job is only affected by global sections residing above it,

and there may be any number of global sections. Specific job definitions

may override any parameter set in global sections.

.SH "JOB PARAMETERS"

.SS Types

Some parameters may take arguments of a specific type. The types used are:

.TP

.I str

String: a sequence of alphanumeric characters.

.TP

.I int

SI integer: a whole number, possibly containing a suffix denoting the base unit

of the value. Accepted suffixes are `k', 'M', 'G', 'T', and 'P', denoting

kilo (1024), mega (1024^2), giga (1024^3), tera (1024^4), and peta (1024^5)

respectively. The suffix is not case sensitive. If prefixed with '0x', the

value is assumed to be base 16 (hexadecimal).

.TP

.I bool

Boolean: a true or false value. `0' denotes false, `1' denotes true.

.TP

.I irange

Integer range: a range of integers specified in the format

\fIlower\fR:\fIupper\fR or \fIlower\fR\-\fIupper\fR. \fIlower\fR and

\fIupper\fR may contain a suffix as described above. If an option allows two

sets of ranges, they are separated with a `,' or `/' character. For example:

`8\-8k/8M\-4G'.

.SS "Parameter List"

.TP

.BI name \fR=\fPstr

May be used to override the job name. On the command line, this parameter

has the special purpose of signalling the start of a new job.

.TP

.BI description \fR=\fPstr

Human-readable description of the job. It is printed when the job is run, but

otherwise has no special purpose.

.TP

.BI directory \fR=\fPstr

Prefix filenames with this directory. Used to place files in a location other

than `./'.

.TP

.BI filename \fR=\fPstr

.B fio

normally makes up a file name based on the job name, thread number, and file

number. If you want to share files between threads in a job or several jobs,

specify a \fIfilename\fR for each of them to override the default. If the I/O

engine used is `net', \fIfilename\fR is the host and port to connect to in the

format \fIhost\fR/\fIport\fR. If the I/O engine is file-based, you can specify

a number of files by separating the names with a `:' character. `\-' is a

reserved name, meaning stdin or stdout, depending on the read/write direction

set.

.TP

.BI lockfile \fR=\fPstr

Fio defaults to not locking any files before it does IO to them. If a file or

file descriptor is shared, fio can serialize IO to that file to make the end

result consistent. This is usual for emulating real workloads that share files.

The lock modes are:

.RS

.RS

.TP

.B none

No locking. This is the default.

.TP

.B exclusive

Only one thread or process may do IO at the time, excluding all others.

.TP

.B readwrite

Read-write locking on the file. Many readers may access the file at the same

time, but writes get exclusive access.

.RE

.P

The option may be post-fixed with a lock batch number. If set, then each

thread/process may do that amount of IOs to the file before giving up the lock.

Since lock acquisition is expensive, batching the lock/unlocks will speed up IO.

.RE

.P

.BI opendir \fR=\fPstr

Recursively open any files below directory \fIstr\fR.

.TP

.BI readwrite \fR=\fPstr "\fR,\fP rw" \fR=\fPstr

Type of I/O pattern. Accepted values are:

.RS

.RS

.TP

.B read

Sequential reads.

.TP

.B write

Sequential writes.

.TP

.B randread

Random reads.

.TP

.B randwrite

Random writes.

.TP

.B rw

Mixed sequential reads and writes.

.TP

.B randrw

Mixed random reads and writes.

.RE

.P

For mixed I/O, the default split is 50/50. For random I/O, the number of I/Os

to perform before getting a new offset can be specified by appending

`:\fIint\fR' to the pattern type. The default is 1.

.RE

.TP

.BI kb_base \fR=\fPint

The base unit for a kilobyte. The defacto base is 2^10, 1024. Storage

manufacturers like to use 10^3 or 1000 as a base ten unit instead, for obvious

reasons. Allow values are 1024 or 1000, with 1024 being the default.

.TP

.BI randrepeat \fR=\fPbool

Seed the random number generator in a predictable way so results are repeatable

across runs. Default: true.

.TP

.BI fallocate \fR=\fPbool

By default, fio will use fallocate() to advise the system of the size of the

file we are going to write. This can be turned off with fallocate=0. May not

be available on all supported platforms.

.TP

.BI fadvise_hint \fR=\fPbool

Disable use of \fIposix_fadvise\fR\|(2) to advise the kernel what I/O patterns

are likely to be issued. Default: true.

.TP

.BI size \fR=\fPint

Total size of I/O for this job. \fBfio\fR will run until this many bytes have

been transfered, unless limited by other options (\fBruntime\fR, for instance).

Unless \fBnr_files\fR and \fBfilesize\fR options are given, this amount will be

divided between the available files for the job.

.TP

.BI fill_device \fR=\fPbool

Sets size to something really large and waits for ENOSPC (no space left on

device) as the terminating condition. Only makes sense with sequential write.

For a read workload, the mount point will be filled first then IO started on

the result.

.TP

.BI filesize \fR=\fPirange

Individual file sizes. May be a range, in which case \fBfio\fR will select sizes

for files at random within the given range, limited to \fBsize\fR in total (if

that is given). If \fBfilesize\fR is not specified, each created file is the

same size.

.TP

.BI blocksize \fR=\fPint[,int] "\fR,\fB bs" \fR=\fPint[,int]

Block size for I/O units. Default: 4k. Values for reads and writes can be

specified seperately in the format \fIread\fR,\fIwrite\fR, either of

which may be empty to leave that value at its default.

.TP

.BI blocksize_range \fR=\fPirange[,irange] "\fR,\fB bsrange" \fR=\fPirange[,irange]

Specify a range of I/O block sizes. The issued I/O unit will always be a

multiple of the minimum size, unless \fBblocksize_unaligned\fR is set. Applies

to both reads and writes if only one range is given, but can be specified

seperately with a comma seperating the values. Example: bsrange=1k-4k,2k-8k.

Also (see \fBblocksize\fR).

.TP

.BI bssplit \fR=\fPstr

This option allows even finer grained control of the block sizes issued,

not just even splits between them. With this option, you can weight various

block sizes for exact control of the issued IO for a job that has mixed

block sizes. The format of the option is bssplit=blocksize/percentage,

optionally adding as many definitions as needed seperated by a colon.

Example: bssplit=4k/10:64k/50:32k/40 would issue 50% 64k blocks, 10% 4k

blocks and 40% 32k blocks. \fBbssplit\fR also supports giving separate

splits to reads and writes. The format is identical to what the

\fBbs\fR option accepts, the read and write parts are separated with a

comma.

.TP

.B blocksize_unaligned\fR,\fP bs_unaligned

If set, any size in \fBblocksize_range\fR may be used. This typically won't

work with direct I/O, as that normally requires sector alignment.

.TP

.BI blockalign \fR=\fPint[,int] "\fR,\fB ba" \fR=\fPint[,int]

At what boundary to align random IO offsets. Defaults to the same as 'blocksize'

the minimum blocksize given. Minimum alignment is typically 512b

for using direct IO, though it usually depends on the hardware block size.

This option is mutually exclusive with using a random map for files, so it

will turn off that option.

.TP

.B zero_buffers

Initialise buffers with all zeros. Default: fill buffers with random data.

.TP

.B refill_buffers

If this option is given, fio will refill the IO buffers on every submit. The

default is to only fill it at init time and reuse that data. Only makes sense

if zero_buffers isn't specified, naturally. If data verification is enabled,

refill_buffers is also automatically enabled.

.TP

.BI nrfiles \fR=\fPint

Number of files to use for this job. Default: 1.

.TP

.BI openfiles \fR=\fPint

Number of files to keep open at the same time. Default: \fBnrfiles\fR.

.TP

.BI file_service_type \fR=\fPstr

Defines how files to service are selected. The following types are defined:

.RS

.RS

.TP

.B random

Choose a file at random

.TP

.B roundrobin

Round robin over open files (default).

.B sequential

Do each file in the set sequentially.

.RE

.P

The number of I/Os to issue before switching a new file can be specified by

appending `:\fIint\fR' to the service type.

.RE

.TP

.BI ioengine \fR=\fPstr

Defines how the job issues I/O. The following types are defined:

.RS

.RS

.TP

.B sync

Basic \fIread\fR\|(2) or \fIwrite\fR\|(2) I/O. \fIfseek\fR\|(2) is used to

position the I/O location.

.TP

.B psync

Basic \fIpread\fR\|(2) or \fIpwrite\fR\|(2) I/O.

.TP

.B vsync

Basic \fIreadv\fR\|(2) or \fIwritev\fR\|(2) I/O. Will emulate queuing by

coalescing adjacents IOs into a single submission.

.TP

.B libaio

Linux native asynchronous I/O.

.TP

.B posixaio

glibc POSIX asynchronous I/O using \fIaio_read\fR\|(3) and \fIaio_write\fR\|(3).

.TP

.B mmap

File is memory mapped with \fImmap\fR\|(2) and data copied using

\fImemcpy\fR\|(3).

.TP

.B splice

\fIsplice\fR\|(2) is used to transfer the data and \fIvmsplice\fR\|(2) to

transfer data from user-space to the kernel.

.TP

.B syslet-rw

Use the syslet system calls to make regular read/write asynchronous.

.TP

.B sg

SCSI generic sg v3 I/O. May be either synchronous using the SG_IO ioctl, or if

the target is an sg character device, we use \fIread\fR\|(2) and

\fIwrite\fR\|(2) for asynchronous I/O.

.TP

.B null

Doesn't transfer any data, just pretends to. Mainly used to exercise \fBfio\fR

itself and for debugging and testing purposes.

.TP

.B net

Transfer over the network. \fBfilename\fR must be set appropriately to

`\fIhost\fR/\fIport\fR' regardless of data direction. If receiving, only the

\fIport\fR argument is used.

.TP

.B netsplice

Like \fBnet\fR, but uses \fIsplice\fR\|(2) and \fIvmsplice\fR\|(2) to map data

and send/receive.

.TP

.B cpuio

Doesn't transfer any data, but burns CPU cycles according to \fBcpuload\fR and

\fBcpucycles\fR parameters.

.TP

.B guasi

The GUASI I/O engine is the Generic Userspace Asynchronous Syscall Interface

approach to asycnronous I/O.

.br

See <http://www.xmailserver.org/guasi\-lib.html>.

.TP

.B external

Loads an external I/O engine object file. Append the engine filename as

`:\fIenginepath\fR'.

.RE

.RE

.TP

.BI iodepth \fR=\fPint

Number of I/O units to keep in flight against the file. Default: 1.

.TP

.BI iodepth_batch \fR=\fPint

Number of I/Os to submit at once. Default: \fBiodepth\fR.

.TP

.BI iodepth_batch_complete \fR=\fPint

This defines how many pieces of IO to retrieve at once. It defaults to 1 which

means that we'll ask for a minimum of 1 IO in the retrieval process from the

kernel. The IO retrieval will go on until we hit the limit set by

\fBiodepth_low\fR. If this variable is set to 0, then fio will always check for

completed events before queuing more IO. This helps reduce IO latency, at the

cost of more retrieval system calls.

.TP

.BI iodepth_low \fR=\fPint

Low watermark indicating when to start filling the queue again. Default:

\fBiodepth\fR.

.TP

.BI direct \fR=\fPbool

If true, use non-buffered I/O (usually O_DIRECT). Default: false.

.TP

.BI buffered \fR=\fPbool

If true, use buffered I/O. This is the opposite of the \fBdirect\fR parameter.

Default: true.

.TP

.BI offset \fR=\fPint

Offset in the file to start I/O. Data before the offset will not be touched.

.TP

.BI fsync \fR=\fPint

How many I/Os to perform before issuing an \fBfsync\fR\|(2) of dirty data. If

0, don't sync. Default: 0.

.TP

.BI fdatasync \fR=\fPint

Like \fBfsync\fR, but uses \fBfdatasync\fR\|(2) instead to only sync the

data parts of the file. Default: 0.

.TP

.BI overwrite \fR=\fPbool

If writing, setup the file first and do overwrites. Default: false.

.TP

.BI end_fsync \fR=\fPbool

Sync file contents when job exits. Default: false.

.TP

.BI fsync_on_close \fR=\fPbool

If true, sync file contents on close. This differs from \fBend_fsync\fR in that

it will happen on every close, not just at the end of the job. Default: false.

.TP

.BI rwmixcycle \fR=\fPint

How many milliseconds before switching between reads and writes for a mixed

workload. Default: 500ms.

.TP

.BI rwmixread \fR=\fPint

Percentage of a mixed workload that should be reads. Default: 50.

.TP

.BI rwmixwrite \fR=\fPint

Percentage of a mixed workload that should be writes. If \fBrwmixread\fR and

\fBrwmixwrite\fR are given and do not sum to 100%, the latter of the two

overrides the first. This may interfere with a given rate setting, if fio is

asked to limit reads or writes to a certain rate. If that is the case, then

the distribution may be skewed. Default: 50.

.TP

.B norandommap

Normally \fBfio\fR will cover every block of the file when doing random I/O. If

this parameter is given, a new offset will be chosen without looking at past

I/O history. This parameter is mutually exclusive with \fBverify\fR.

.TP

.B softrandommap

See \fBnorandommap\fR. If fio runs with the random block map enabled and it

fails to allocate the map, if this option is set it will continue without a

random block map. As coverage will not be as complete as with random maps, this

option is disabled by default.

.TP

.BI nice \fR=\fPint

Run job with given nice value. See \fInice\fR\|(2).

.TP

.BI prio \fR=\fPint

Set I/O priority value of this job between 0 (highest) and 7 (lowest). See

\fIionice\fR\|(1).

.TP

.BI prioclass \fR=\fPint

Set I/O priority class. See \fIionice\fR\|(1).

.TP

.BI thinktime \fR=\fPint

Stall job for given number of microseconds between issuing I/Os.

.TP

.BI thinktime_spin \fR=\fPint

Pretend to spend CPU time for given number of microseconds, sleeping the rest

of the time specified by \fBthinktime\fR. Only valid if \fBthinktime\fR is set.

.TP

.BI thinktime_blocks \fR=\fPint

Number of blocks to issue before waiting \fBthinktime\fR microseconds.

Default: 1.

.TP

.BI rate \fR=\fPint

Cap bandwidth used by this job. The number is in bytes/sec, the normal postfix

rules apply. You can use \fBrate\fR=500k to limit reads and writes to 500k each,

or you can specify read and writes separately. Using \fBrate\fR=1m,500k would

limit reads to 1MB/sec and writes to 500KB/sec. Capping only reads or writes

can be done with \fBrate\fR=,500k or \fBrate\fR=500k,. The former will only

limit writes (to 500KB/sec), the latter will only limit reads.

.TP

.BI ratemin \fR=\fPint

Tell \fBfio\fR to do whatever it can to maintain at least the given bandwidth.

Failing to meet this requirement will cause the job to exit. The same format

as \fBrate\fR is used for read vs write separation.

.TP

.BI rate_iops \fR=\fPint

Cap the bandwidth to this number of IOPS. Basically the same as rate, just

specified independently of bandwidth. The same format as \fBrate\fR is used for

read vs write seperation. If \fBblocksize\fR is a range, the smallest block

size is used as the metric.

.TP

.BI rate_iops_min \fR=\fPint

If this rate of I/O is not met, the job will exit. The same format as \fBrate\fR

is used for read vs write seperation.

.TP

.BI ratecycle \fR=\fPint

Average bandwidth for \fBrate\fR and \fBratemin\fR over this number of

milliseconds. Default: 1000ms.

.TP

.BI cpumask \fR=\fPint

Set CPU affinity for this job. \fIint\fR is a bitmask of allowed CPUs the job

may run on. See \fBsched_setaffinity\fR\|(2).

.TP

.BI cpus_allowed \fR=\fPstr

Same as \fBcpumask\fR, but allows a comma-delimited list of CPU numbers.

.TP

.BI startdelay \fR=\fPint

Delay start of job for the specified number of seconds.

.TP

.BI runtime \fR=\fPint

Terminate processing after the specified number of seconds.

.TP

.B time_based

If given, run for the specified \fBruntime\fR duration even if the files are

completely read or written. The same workload will be repeated as many times

as \fBruntime\fR allows.

.TP

.BI ramp_time \fR=\fPint

If set, fio will run the specified workload for this amount of time before

logging any performance numbers. Useful for letting performance settle before

logging results, thus minimizing the runtime required for stable results. Note

that the \fBramp_time\fR is considered lead in time for a job, thus it will

increase the total runtime if a special timeout or runtime is specified.

.TP

.BI invalidate \fR=\fPbool

Invalidate buffer-cache for the file prior to starting I/O. Default: true.

.TP

.BI sync \fR=\fPbool

Use synchronous I/O for buffered writes. For the majority of I/O engines,

this means using O_SYNC. Default: false.

.TP

.BI iomem \fR=\fPstr "\fR,\fP mem" \fR=\fPstr

Allocation method for I/O unit buffer. Allowed values are:

.RS

.RS

.TP

.B malloc

Allocate memory with \fImalloc\fR\|(3).

.TP

.B shm

Use shared memory buffers allocated through \fIshmget\fR\|(2).

.TP

.B shmhuge

Same as \fBshm\fR, but use huge pages as backing.

.TP

.B mmap

Use \fImmap\fR\|(2) for allocation. Uses anonymous memory unless a filename

is given after the option in the format `:\fIfile\fR'.

.TP

.B mmaphuge

Same as \fBmmap\fR, but use huge files as backing.

.RE

.P

The amount of memory allocated is the maximum allowed \fBblocksize\fR for the

job multiplied by \fBiodepth\fR. For \fBshmhuge\fR or \fBmmaphuge\fR to work,

the system must have free huge pages allocated. \fBmmaphuge\fR also needs to

have hugetlbfs mounted, and \fIfile\fR must point there. At least on Linux,

huge pages must be manually allocated. See \fB/proc/sys/vm/nr_hugehages\fR

and the documentation for that. Normally you just need to echo an appropriate

number, eg echoing 8 will ensure that the OS has 8 huge pages ready for

use.

.RE

.TP

.BI iomem_align \fR=\fPint

This indiciates the memory alignment of the IO memory buffers. Note that the

given alignment is applied to the first IO unit buffer, if using \fBiodepth\fR

the alignment of the following buffers are given by the \fBbs\fR used. In

other words, if using a \fBbs\fR that is a multiple of the page sized in the

system, all buffers will be aligned to this value. If using a \fBbs\fR that

is not page aligned, the alignment of subsequent IO memory buffers is the

sum of the \fBiomem_align\fR and \fBbs\fR used.

.TP

.BI hugepage\-size \fR=\fPint

Defines the size of a huge page. Must be at least equal to the system setting.

Should be a multiple of 1MB. Default: 4MB.

.TP

.B exitall

Terminate all jobs when one finishes. Default: wait for each job to finish.

.TP

.BI bwavgtime \fR=\fPint

Average bandwidth calculations over the given time in milliseconds. Default:

500ms.

.TP

.BI create_serialize \fR=\fPbool

If true, serialize file creation for the jobs. Default: true.

.TP

.BI create_fsync \fR=\fPbool

\fIfsync\fR\|(2) data file after creation. Default: true.

.TP

.BI create_on_open \fR=\fPbool

If true, the files are not created until they are opened for IO by the job.

.TP

.BI pre_read \fR=\fPbool

If this is given, files will be pre-read into memory before starting the given

IO operation. This will also clear the \fR \fBinvalidate\fR flag, since it is

pointless to pre-read and then drop the cache. This will only work for IO

engines that are seekable, since they allow you to read the same data

multiple times. Thus it will not work on eg network or splice IO.

.TP

.BI unlink \fR=\fPbool

Unlink job files when done. Default: false.

.TP

.BI loops \fR=\fPint

Specifies the number of iterations (runs of the same workload) of this job.

Default: 1.

.TP

.BI do_verify \fR=\fPbool

Run the verify phase after a write phase. Only valid if \fBverify\fR is set.

Default: true.

.TP

.BI verify \fR=\fPstr

Method of verifying file contents after each iteration of the job. Allowed

values are:

.RS

.RS

.TP

.B md5 crc16 crc32 crc32c crc32c-intel crc64 crc7 sha256 sha512 sha1

Store appropriate checksum in the header of each block.

.TP

.B meta

Write extra information about each I/O (timestamp, block number, etc.). The

block number is verified.

.TP

.B pattern

Fill I/O buffers with a specific pattern that is used to verify. If the pattern

is < 4bytes, it can either be a decimal or a hexadecimal number. If the pattern

is > 4bytes, currently, it can only be a hexadecimal pattern starting with

either "0x" or "0X".

.TP

.B null

Pretend to verify. Used for testing internals.

.RE

This option can be used for repeated burn-in tests of a system to make sure

that the written data is also correctly read back. If the data direction given

is a read or random read, fio will assume that it should verify a previously

written file. If the data direction includes any form of write, the verify will

be of the newly written data.

.RE

.TP

.BI verify_sort \fR=\fPbool

If true, written verify blocks are sorted if \fBfio\fR deems it to be faster to

read them back in a sorted manner. Default: true.

.TP

.BI verify_offset \fR=\fPint

Swap the verification header with data somewhere else in the block before

writing. It is swapped back before verifying.

.TP

.BI verify_interval \fR=\fPint

Write the verification header for this number of bytes, which should divide

\fBblocksize\fR. Default: \fBblocksize\fR.

.TP

.BI verify_fatal \fR=\fPbool

If true, exit the job on the first observed verification failure. Default:

false.

.TP

.BI verify_async \fR=\fPint

Fio will normally verify IO inline from the submitting thread. This option

takes an integer describing how many async offload threads to create for IO

verification instead, causing fio to offload the duty of verifying IO contents

to one or more separate threads. If using this offload option, even sync IO

engines can benefit from using an \fBiodepth\fR setting higher than 1, as it

allows them to have IO in flight while verifies are running.

.TP

.BI verify_async_cpus \fR=\fPstr

Tell fio to set the given CPU affinity on the async IO verification threads.

See \fBcpus_allowed\fP for the format used.

.TP

.B stonewall

Wait for preceeding jobs in the job file to exit before starting this one.

\fBstonewall\fR implies \fBnew_group\fR.

.TP

.B new_group

Start a new reporting group. If not given, all jobs in a file will be part

of the same reporting group, unless separated by a stonewall.

.TP

.BI numjobs \fR=\fPint

Number of clones (processes/threads performing the same workload) of this job.

Default: 1.

.TP

.B group_reporting

If set, display per-group reports instead of per-job when \fBnumjobs\fR is

specified.

.TP

.B thread

Use threads created with \fBpthread_create\fR\|(3) instead of processes created

with \fBfork\fR\|(2).

.TP

.BI zonesize \fR=\fPint

Divide file into zones of the specified size in bytes. See \fBzoneskip\fR.

.TP

.BI zoneskip \fR=\fPint

Skip the specified number of bytes when \fBzonesize\fR bytes of data have been

read.

.TP

.BI write_iolog \fR=\fPstr

Write the issued I/O patterns to the specified file.

.TP

.BI read_iolog \fR=\fPstr

Replay the I/O patterns contained in the specified file generated by

\fBwrite_iolog\fR, or may be a \fBblktrace\fR binary file.

.TP

.B write_bw_log \fR=\fPstr

If given, write a bandwidth log of the jobs in this job file. Can be used to

store data of the bandwidth of the jobs in their lifetime. The included

fio_generate_plots script uses gnuplot to turn these text files into nice

graphs. See \fBwrite_log_log\fR for behaviour of given filename. For this

option, the postfix is _bw.log.

.TP

.B write_lat_log

Same as \fBwrite_bw_log\fR, but writes I/O completion latencies. If no

filename is given with this option, the default filename of "jobname_type.log"

is used. Even if the filename is given, fio will still append the type of log.

.TP

.B disable_clat \fR=\fPbool

Disable measurements of completion latency numbers. Useful only for cutting

back the number of calls to gettimeofday, as that does impact performance at

really high IOPS rates. Note that to really get rid of a large amount of these

calls, this option must be used with disable_slat and disable_bw as well.

.TP

.B disable_slat \fR=\fPbool

Disable measurements of submission latency numbers. See \fBdisable_clat\fR.

.TP

.B disable_bw_measurement \fR=\fPbool

Disable measurements of throughput/bandwidth numbers. See \fBdisable_clat\fR.

.TP

.BI lockmem \fR=\fPint

Pin the specified amount of memory with \fBmlock\fR\|(2). Can be used to

simulate a smaller amount of memory.

.TP

.BI exec_prerun \fR=\fPstr

Before running the job, execute the specified command with \fBsystem\fR\|(3).

.TP

.BI exec_postrun \fR=\fPstr

Same as \fBexec_prerun\fR, but the command is executed after the job completes.

.TP

.BI ioscheduler \fR=\fPstr

Attempt to switch the device hosting the file to the specified I/O scheduler.

.TP

.BI cpuload \fR=\fPint

If the job is a CPU cycle-eater, attempt to use the specified percentage of

CPU cycles.

.TP

.BI cpuchunks \fR=\fPint

If the job is a CPU cycle-eater, split the load into cycles of the

given time in milliseconds.

.TP

.BI disk_util \fR=\fPbool

Generate disk utilization statistics if the platform supports it. Default: true.

.TP

.BI gtod_reduce \fR=\fPbool

Enable all of the gettimeofday() reducing options (disable_clat, disable_slat,

disable_bw) plus reduce precision of the timeout somewhat to really shrink the

gettimeofday() call count. With this option enabled, we only do about 0.4% of

the gtod() calls we would have done if all time keeping was enabled.

.TP

.BI gtod_cpu \fR=\fPint

Sometimes it's cheaper to dedicate a single thread of execution to just getting

the current time. Fio (and databases, for instance) are very intensive on

gettimeofday() calls. With this option, you can set one CPU aside for doing

nothing but logging current time to a shared memory location. Then the other

threads/processes that run IO workloads need only copy that segment, instead of

entering the kernel with a gettimeofday() call. The CPU set aside for doing

these time calls will be excluded from other uses. Fio will manually clear it

from the CPU mask of other jobs.

.TP

.BI cgroup \fR=\fPstr

Add job to this control group. If it doesn't exist, it will be created.

The system must have a mounted cgroup blkio mount point for this to work. If

your system doesn't have it mounted, you can do so with:

# mount -t cgroup -o blkio none /cgroup

.TP

.BI cgroup_weight \fR=\fPint

Set the weight of the cgroup to this value. See the documentation that comes

with the kernel, allowed values are in the range of 100..1000.

.TP

.BI uid \fR=\fPint

Instead of running as the invoking user, set the user ID to this value before

the thread/process does any work.

.TP

.BI gid \fR=\fPint

Set group ID, see \fBuid\fR.

.SH OUTPUT

While running, \fBfio\fR will display the status of the created jobs. For

example:

.RS

.P

Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]

.RE

.P

The characters in the first set of brackets denote the current status of each

threads. The possible values are:

.P

.PD 0

.RS

.TP

.B P

Setup but not started.

.TP

.B C

Thread created.

.TP

.B I

Initialized, waiting.

.TP

.B R

Running, doing sequential reads.

.TP

.B r

Running, doing random reads.

.TP

.B W

Running, doing sequential writes.

.TP

.B w

Running, doing random writes.

.TP

.B M

Running, doing mixed sequential reads/writes.

.TP

.B m

Running, doing mixed random reads/writes.

.TP

.B F

Running, currently waiting for \fBfsync\fR\|(2).

.TP

.B V

Running, verifying written data.

.TP

.B E

Exited, not reaped by main thread.

.TP

.B \-

Exited, thread reaped.

.RE

.PD

.P

The second set of brackets shows the estimated completion percentage of

the current group. The third set shows the read and write I/O rate,

respectively. Finally, the estimated run time of the job is displayed.

.P

When \fBfio\fR completes (or is interrupted by Ctrl-C), it will show data

for each thread, each group of threads, and each disk, in that order.

.P

Per-thread statistics first show the threads client number, group-id, and

error code. The remaining figures are as follows:

.RS

.TP

.B io

Number of megabytes of I/O performed.

.TP

.B bw

Average data rate (bandwidth).

.TP

.B runt

Threads run time.

.TP

.B slat

Submission latency minimum, maximum, average and standard deviation. This is

the time it took to submit the I/O.

.TP

.B clat

Completion latency minimum, maximum, average and standard deviation. This

is the time between submission and completion.

.TP

.B bw

Bandwidth minimum, maximum, percentage of aggregate bandwidth received, average

and standard deviation.

.TP

.B cpu

CPU usage statistics. Includes user and system time, number of context switches

this thread went through and number of major and minor page faults.

.TP

.B IO depths

Distribution of I/O depths. Each depth includes everything less than (or equal)

to it, but greater than the previous depth.

.TP

.B IO issued

Number of read/write requests issued, and number of short read/write requests.

.TP

.B IO latencies

Distribution of I/O completion latencies. The numbers follow the same pattern

as \fBIO depths\fR.

.RE

.P

The group statistics show:

.PD 0

.RS

.TP

.B io

Number of megabytes I/O performed.

.TP

.B aggrb

Aggregate bandwidth of threads in the group.

.TP

.B minb

Minimum average bandwidth a thread saw.

.TP

.B maxb

Maximum average bandwidth a thread saw.

.TP

.B mint

Shortest runtime of threads in the group.

.TP

.B maxt

Longest runtime of threads in the group.

.RE

.PD

.P

Finally, disk statistics are printed with reads first:

.PD 0

.RS

.TP

.B ios

Number of I/Os performed by all groups.

.TP

.B merge

Number of merges in the I/O scheduler.

.TP

.B ticks

Number of ticks we kept the disk busy.

.TP

.B io_queue

Total time spent in the disk queue.

.TP

.B util

Disk utilization.

.RE

.PD

.SH TERSE OUTPUT

If the \fB\-\-minimal\fR option is given, the results will be printed in a

semicolon-delimited format suitable for scripted use. The fields are:

.P

.RS

.B jobname, groupid, error

.P

Read status:

.RS

.B KB I/O, bandwidth \fR(KB/s)\fP, runtime \fR(ms)\fP

.P

Submission latency:

.RS

.B min, max, mean, standard deviation

.RE

Completion latency:

.RS

.B min, max, mean, standard deviation

.RE

Bandwidth:

.RS

.B min, max, aggregate percentage of total, mean, standard deviation

.RE

.RE

.P

Write status:

.RS

.B KB I/O, bandwidth \fR(KB/s)\fP, runtime \fR(ms)\fP

.P

Submission latency:

.RS

.B min, max, mean, standard deviation

.RE

Completion latency:

.RS

.B min, max, mean, standard deviation

.RE

Bandwidth:

.RS

.B min, max, aggregate percentage of total, mean, standard deviation

.RE

.RE

.P

CPU usage:

.RS

.B user, system, context switches, major page faults, minor page faults

.RE

.P

IO depth distribution:

.RS

.B <=1, 2, 4, 8, 16, 32, >=64

.RE

.P

IO latency distribution (ms):

.RS

.B <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000

.RE

.P

.B text description

.RE

.SH AUTHORS

.B fio

was written by Jens Axboe <jens.axboe@oracle.com>.

.br

This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au> based

on documentation by Jens Axboe.

.SH "REPORTING BUGS"

Report bugs to the \fBfio\fR mailing list <fio@vger.kernel.org>.

See \fBREADME\fR.

.SH "SEE ALSO"

For further documentation see \fBHOWTO\fR and \fBREADME\fR.

.br

Sample jobfiles are available in the \fBexamples\fR directory.