NAME
fio - flexible I/O tester
SYNOPSIS
fio [options] [jobfile]...
DESCRIPTION
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.
OPTIONS
--output=filename
Write output to filename.
--timeout=timeout
Limit run time to timeout seconds.
--latency-log
Generate per-job latency logs.
--bandwidth-log
Generate per-job bandwidth logs.
--minimal
Print statistics in a terse, semicolon-delimited format.
--showcmd=jobfile
Convert jobfile to a set of command-line options.
--readonly
Enable read-only safety checks.
--eta=when
Specifies when real-time ETA estimate should be printed. when
may be one of `always', `never' or `auto'.
--section=sec
Only run section sec from job file.
--cmdhelp=command
Print help information for command. May be `all' for all
commands.
--debug=type
Enable verbose tracing of various fio actions. May be `all' for
all types or individual types separated by a comma (eg
--debug=io,file). `help' will list all available tracing
options.
--help Display usage information and exit.
--version
Display version information and exit.
--terse-version=type
Terse version output format
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.
If jobfile is specified as `-', the job file will be read from standard
input.
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.
JOB PARAMETERS
Types
Some parameters may take arguments of a specific type. The types used
are:
str String: a sequence of alphanumeric characters.
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). A suffix may
include a trailing 'b', for instance 'kb' is identical to 'k'.
You can specify a base 10 value by using 'KiB', 'MiB', 'GiB',
etc. This is useful for disk drives where values are often given
in base 10 values. Specifying '30GiB' will get you 30*1000^3
bytes.
bool Boolean: a true or false value. `0' denotes false, `1' denotes
true.
irange Integer range: a range of integers specified in the format
lower:upper or lower-upper. lower and upper 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'.
float_list
List of floating numbers: A list of floating numbers, separated
by a ':' charcater.
Parameter List
name=str
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.
description=str
Human-readable description of the job. It is printed when the
job is run, but otherwise has no special purpose.
directory=str
Prefix filenames with this directory. Used to place files in a
location other than `./'.
filename=str
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 filename for each of
them to override the default. If the I/O engine used is `net',
filename is the host and port to connect to in the format
host/port. 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.
lockfile=str
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:
none No locking. This is the default.
exclusive
Only one thread or process may do IO at the time,
excluding all others.
readwrite
Read-write locking on the file. Many readers may
access the file at the same time, but writes get
exclusive access.
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.
opendir=str Recursively open any files below directory str.
readwrite=str, rw=str
Type of I/O pattern. Accepted values are:
read Sequential reads.
write Sequential writes.
randread
Random reads.
randwrite
Random writes.
rw Mixed sequential reads and writes.
randrw Mixed random reads and writes.
For mixed I/O, the default split is 50/50. For certain types of
io the result may still be skewed a bit, since the speed may be
different. It is possible to specify a number of IO's to do
before getting a new offset, this is one by appending a `:<nr>
to the end of the string given. For a random read, it would look
like rw=randread:8 for passing in an offset modifier with a
value of 8. If the postfix is used with a sequential IO pattern,
then the value specified will be added to the generated offset
for each IO. For instance, using rw=write:4k will skip 4k for
every write. It turns sequential IO into sequential IO with
holes. See the rw_sequencer option.
rw_sequencer=str
If an offset modifier is given by appending a number to the
rw=<str> line, then this option controls how that number
modifies the IO offset being generated. Accepted values are:
sequential
Generate sequential offset
identical
Generate the same offset
sequential is only useful for random IO, where fio would
normally generate a new random offset for every IO. If you
append eg 8 to randread, you would get a new random offset for
every 8 IO's. The result would be a seek for only every 8 IO's,
instead of for every IO. Use rw=randread:8 to specify that. As
sequential IO is already sequential, setting sequential for that
would not result in any differences. identical behaves in a
similar fashion, except it sends the same offset 8 number of
times before generating a new offset.
kb_base=int
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.
randrepeat=bool
Seed the random number generator in a predictable way so results
are repeatable across runs. Default: true.
use_os_rand=bool
Fio can either use the random generator supplied by the OS to
generator random offsets, or it can use it's own internal
generator (based on Tausworthe). Default is to use the internal
generator, which is often of better quality and faster. Default:
false.
fallocate=str
Whether pre-allocation is performed when laying down files.
Accepted values are:
none Do not pre-allocate space.
posix Pre-allocate via posix_fallocate().
keep Pre-allocate via fallocate() with
FALLOC_FL_KEEP_SIZE set.
0 Backward-compatible alias for 'none'.
1 Backward-compatible alias for 'posix'.
May not be available on all supported platforms. 'keep' is only
available on Linux. If using ZFS on Solaris this must be set to
'none' because ZFS doesn't support it. Default: 'posix'.
fadvise_hint=bool
Disable use of posix_fadvise(2) to advise the kernel what I/O
patterns are likely to be issued. Default: true.
size=int
Total size of I/O for this job. fio will run until this many
bytes have been transfered, unless limited by other options
(runtime, for instance). Unless nrfiles and filesize options
are given, this amount will be divided between the available
files for the job. If not set, fio will use the full size of the
given files or devices. If the the files do not exist, size must
be given. It is also possible to give size as a percentage
between 1 and 100. If size=20% is given, fio will use 20% of the
full size of the given files or devices.
fill_device=bool, fill_fs=bool
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. This
option doesn't make sense if operating on a raw device node,
since the size of that is already known by the file system.
Additionally, writing beyond end-of-device will not return
ENOSPC there.
filesize=irange
Individual file sizes. May be a range, in which case fio will
select sizes for files at random within the given range, limited
to size in total (if that is given). If filesize is not
specified, each created file is the same size.
blocksize=int[,int], bs=int[,int]
Block size for I/O units. Default: 4k. Values for reads and
writes can be specified separately in the format read,write,
either of which may be empty to leave that value at its default.
blocksize_range=irange[,irange], bsrange=irange[,irange]
Specify a range of I/O block sizes. The issued I/O unit will
always be a multiple of the minimum size, unless
blocksize_unaligned is set. Applies to both reads and writes if
only one range is given, but can be specified separately with a
comma seperating the values. Example: bsrange=1k-4k,2k-8k. Also
(see blocksize).
bssplit=str
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 separated by a colon. Example:
bssplit=4k/10:64k/50:32k/40 would issue 50% 64k blocks, 10% 4k
blocks and 40% 32k blocks. bssplit also supports giving separate
splits to reads and writes. The format is identical to what the
bs option accepts, the read and write parts are separated with a
comma.
blocksize_unaligned, bs_unaligned
If set, any size in blocksize_range may be used. This typically
won't work with direct I/O, as that normally requires sector
alignment.
blockalign=int[,int], ba=int[,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.
zero_buffers
Initialise buffers with all zeros. Default: fill buffers with
random data.
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.
scramble_buffers=bool
If refill_buffers is too costly and the target is using data
deduplication, then setting this option will slightly modify the
IO buffer contents to defeat normal de-dupe attempts. This is
not enough to defeat more clever block compression attempts, but
it will stop naive dedupe of blocks. Default: true.
nrfiles=int
Number of files to use for this job. Default: 1.
openfiles=int
Number of files to keep open at the same time. Default:
nrfiles.
file_service_type=str
Defines how files to service are selected. The following types
are defined:
random Choose a file at random
roundrobin
Round robin over open files (default). sequential
Do each file in the set sequentially.
The number of I/Os to issue before switching a new file can be
specified by appending `:int' to the service type.
ioengine=str
Defines how the job issues I/O. The following types are
defined:
sync Basic read(2) or write(2) I/O. fseek(2) is used
to position the I/O location.
psync Basic pread(2) or pwrite(2) I/O.
vsync Basic readv(2) or writev(2) I/O. Will emulate
queuing by coalescing adjacents IOs into a single
submission.
libaio Linux native asynchronous I/O. This engine also
has a sub-option, userspace_reap. To set it, use
ioengine=libaio:userspace_reap. Normally, with
the libaio engine in use, fio will use the
io_getevents(3) system call to reap newly returned
events. With this flag turned on, the AIO ring
will be read directly from user-space to reap
events. The reaping mode is only enabled when
polling for a minimum of 0 events (eg when
iodepth_batch_complete=0).
posixaio
POSIX asynchronous I/O using aio_read(3) and
aio_write(3).
solarisaio
Solaris native asynchronous I/O.
windowsaio
Windows native asynchronous I/O.
mmap File is memory mapped with mmap(2) and data copied
using memcpy(3).
splice splice(2) is used to transfer the data and
vmsplice(2) to transfer data from user-space to
the kernel.
syslet-rw
Use the syslet system calls to make regular
read/write asynchronous.
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 read(2) and write(2) for
asynchronous I/O.
null Doesn't transfer any data, just pretends to.
Mainly used to exercise fio itself and for
debugging and testing purposes.
net Transfer over the network. filename must be set
appropriately to `host/port' regardless of data
direction. If receiving, only the port argument
is used.
netsplice
Like net, but uses splice(2) and vmsplice(2) to
map data and send/receive.
cpuio Doesn't transfer any data, but burns CPU cycles
according to cpuload and cpucycles parameters.
guasi The GUASI I/O engine is the Generic Userspace
Asynchronous Syscall Interface approach to
asycnronous I/O.
See <http://www.xmailserver.org/guasi-lib.html>.
rdma The RDMA I/O engine supports both RDMA memory
semantics (RDMA_WRITE/RDMA_READ) and channel
semantics (Send/Recv) for the InfiniBand, RoCE and
iWARP protocols.
external
Loads an external I/O engine object file. Append
the engine filename as `:enginepath'.
iodepth=int
Number of I/O units to keep in flight against the file. Note
that increasing iodepth beyond 1 will not affect synchronous
ioengines (except for small degress when verify_async is in
use). Even async engines my impose OS restrictions causing the
desired depth not to be achieved. This may happen on Linux when
using libaio and not setting direct=1, since buffered IO is not
async on that OS. Keep an eye on the IO depth distribution in
the fio output to verify that the achieved depth is as expected.
Default: 1.
iodepth_batch=int
Number of I/Os to submit at once. Default: iodepth.
iodepth_batch_complete=int
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 iodepth_low. 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.
iodepth_low=int
Low watermark indicating when to start filling the queue again.
Default: iodepth.
direct=bool
If true, use non-buffered I/O (usually O_DIRECT). Default:
false.
buffered=bool
If true, use buffered I/O. This is the opposite of the direct
parameter. Default: true.
offset=int
Offset in the file to start I/O. Data before the offset will not
be touched.
fsync=int
How many I/Os to perform before issuing an fsync(2) of dirty
data. If 0, don't sync. Default: 0.
fdatasync=int
Like fsync, but uses fdatasync(2) instead to only sync the data
parts of the file. Default: 0.
sync_file_range=str:int
Use sync_file_range() for every val number of write operations.
Fio will track range of writes that have happened since the last
sync_file_range() call. str can currently be one or more of:
wait_before
SYNC_FILE_RANGE_WAIT_BEFORE
write SYNC_FILE_RANGE_WRITE
wait_after
SYNC_FILE_RANGE_WRITE
So if you do sync_file_range=wait_before,write:8, fio
would use
SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for every 8
writes. Also see the sync_file_range(2) man page. This option
is Linux specific.
overwrite=bool
If writing, setup the file first and do overwrites. Default:
false.
end_fsync=bool
Sync file contents when job exits. Default: false.
fsync_on_close=bool
If true, sync file contents on close. This differs from
end_fsync in that it will happen on every close, not just at the
end of the job. Default: false.
rwmixcycle=int
How many milliseconds before switching between reads and writes
for a mixed workload. Default: 500ms.
rwmixread=int
Percentage of a mixed workload that should be reads. Default:
50.
rwmixwrite=int
Percentage of a mixed workload that should be writes. If
rwmixread and rwmixwrite 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.
norandommap
Normally fio 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 verify.
softrandommap=bool
See norandommap. 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.
nice=int
Run job with given nice value. See nice(2).
prio=int
Set I/O priority value of this job between 0 (highest) and 7
(lowest). See ionice(1).
prioclass=int
Set I/O priority class. See ionice(1).
thinktime=int
Stall job for given number of microseconds between issuing I/Os.
thinktime_spin=int
Pretend to spend CPU time for given number of microseconds,
sleeping the rest of the time specified by thinktime. Only
valid if thinktime is set.
thinktime_blocks=int
Number of blocks to issue before waiting thinktime microseconds.
Default: 1.
rate=int
Cap bandwidth used by this job. The number is in bytes/sec, the
normal postfix rules apply. You can use rate=500k to limit reads
and writes to 500k each, or you can specify read and writes
separately. Using rate=1m,500k would limit reads to 1MB/sec and
writes to 500KB/sec. Capping only reads or writes can be done
with rate=,500k or rate=500k,. The former will only limit writes
(to 500KB/sec), the latter will only limit reads.
ratemin=int
Tell fio 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 rate is used for read vs write
separation.
rate_iops=int
Cap the bandwidth to this number of IOPS. Basically the same as
rate, just specified independently of bandwidth. The same format
as rate is used for read vs write seperation. If blocksize is a
range, the smallest block size is used as the metric.
rate_iops_min=int
If this rate of I/O is not met, the job will exit. The same
format as rate is used for read vs write seperation.
ratecycle=int
Average bandwidth for rate and ratemin over this number of
milliseconds. Default: 1000ms.
cpumask=int
Set CPU affinity for this job. int is a bitmask of allowed CPUs
the job may run on. See sched_setaffinity(2).
cpus_allowed=str
Same as cpumask, but allows a comma-delimited list of CPU
numbers.
startdelay=int
Delay start of job for the specified number of seconds.
runtime=int
Terminate processing after the specified number of seconds.
time_based
If given, run for the specified runtime duration even if the
files are completely read or written. The same workload will be
repeated as many times as runtime allows.
ramp_time=int
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 ramp_time is
considered lead in time for a job, thus it will increase the
total runtime if a special timeout or runtime is specified.
invalidate=bool
Invalidate buffer-cache for the file prior to starting I/O.
Default: true.
sync=bool
Use synchronous I/O for buffered writes. For the majority of
I/O engines, this means using O_SYNC. Default: false.
iomem=str, mem=str
Allocation method for I/O unit buffer. Allowed values are:
malloc Allocate memory with malloc(3).
shm Use shared memory buffers allocated through
shmget(2).
shmhuge
Same as shm, but use huge pages as backing.
mmap Use mmap(2) for allocation. Uses anonymous memory
unless a filename is given after the option in the
format `:file'.
mmaphuge
Same as mmap, but use huge files as backing.
The amount of memory allocated is the maximum allowed blocksize
for the job multiplied by iodepth. For shmhuge or mmaphuge to
work, the system must have free huge pages allocated. mmaphuge
also needs to have hugetlbfs mounted, and file must point there.
At least on Linux, huge pages must be manually allocated. See
/proc/sys/vm/nr_hugehages 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.
iomem_align=int, mem_align=int
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 iodepth the alignment of the following buffers
are given by the bs used. In other words, if using a bs that is
a multiple of the page sized in the system, all buffers will be
aligned to this value. If using a bs that is not page aligned,
the alignment of subsequent IO memory buffers is the sum of the
iomem_align and bs used.
hugepage-size=int
Defines the size of a huge page. Must be at least equal to the
system setting. Should be a multiple of 1MB. Default: 4MB.
exitall
Terminate all jobs when one finishes. Default: wait for each
job to finish.
bwavgtime=int
Average bandwidth calculations over the given time in
milliseconds. Default: 500ms.
create_serialize=bool
If true, serialize file creation for the jobs. Default: true.
create_fsync=bool
fsync(2) data file after creation. Default: true.
create_on_open=bool
If true, the files are not created until they are opened for IO
by the job.
pre_read=bool
If this is given, files will be pre-read into memory before
starting the given IO operation. This will also clear the
invalidate 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.
unlink=bool
Unlink job files when done. Default: false.
loops=int
Specifies the number of iterations (runs of the same workload)
of this job. Default: 1.
do_verify=bool
Run the verify phase after a write phase. Only valid if verify
is set. Default: true.
verify=str
Method of verifying file contents after each iteration of the
job. Allowed values are:
md5 crc16 crc32 crc32c crc32c-intel crc64 crc7 sha256
sha512 sha1
Store appropriate checksum in the header of each
block. crc32c-intel is hardware accelerated SSE4.2
driven, falls back to regular crc32c if not
supported by the system.
meta Write extra information about each I/O (timestamp,
block number, etc.). The block number is verified.
See verify_pattern as well.
null Pretend to verify. Used for testing internals.
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.
verify_sort=bool
If true, written verify blocks are sorted if fio deems it to be
faster to read them back in a sorted manner. Default: true.
verify_offset=int
Swap the verification header with data somewhere else in the
block before writing. It is swapped back before verifying.
verify_interval=int
Write the verification header for this number of bytes, which
should divide blocksize. Default: blocksize.
verify_pattern=str
If set, fio will fill the io buffers with this pattern. Fio
defaults to filling with totally random bytes, but sometimes
it's interesting to fill with a known pattern for io
verification purposes. Depending on the width of the pattern,
fio will fill 1/2/3/4 bytes of the buffer at the time(it can be
either a decimal or a hex number). The verify_pattern if larger
than a 32-bit quantity has to be a hex number that starts with
either "0x" or "0X". Use with verify=meta.
verify_fatal=bool
If true, exit the job on the first observed verification
failure. Default: false.
verify_dump=bool
If set, dump the contents of both the original data block and
the data block we read off disk to files. This allows later
analysis to inspect just what kind of data corruption occurred.
On by default.
verify_async=int
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 iodepth setting higher than 1,
as it allows them to have IO in flight while verifies are
running.
verify_async_cpus=str
Tell fio to set the given CPU affinity on the async IO
verification threads. See cpus_allowed for the format used.
verify_backlog=int
Fio will normally verify the written contents of a job that
utilizes verify once that job has completed. In other words,
everything is written then everything is read back and verified.
You may want to verify continually instead for a variety of
reasons. Fio stores the meta data associated with an IO block in
memory, so for large verify workloads, quite a bit of memory
would be used up holding this meta data. If this option is
enabled, fio will write only N blocks before verifying these
blocks.
verify_backlog_batch=int
Control how many blocks fio will verify if verify_backlog is
set. If not set, will default to the value of verify_backlog
(meaning the entire queue is read back and verified). If
verify_backlog_batch is less than verify_backlog then not all
blocks will be verified, if verify_backlog_batch is larger than
verify_backlog, some blocks will be verified more than once.
stonewall , wait_for_previous
Wait for preceding jobs in the job file to exit before starting
this one. stonewall implies new_group.
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.
numjobs=int
Number of clones (processes/threads performing the same
workload) of this job. Default: 1.
group_reporting
If set, display per-group reports instead of per-job when
numjobs is specified.
thread Use threads created with pthread_create(3) instead of processes
created with fork(2).
zonesize=int
Divide file into zones of the specified size in bytes. See
zoneskip.
zoneskip=int
Skip the specified number of bytes when zonesize bytes of data
have been read.
write_iolog=str
Write the issued I/O patterns to the specified file. Specify a
separate file for each job, otherwise the iologs will be
interspersed and the file may be corrupt.
read_iolog=str
Replay the I/O patterns contained in the specified file
generated by write_iolog, or may be a blktrace binary file.
replay_no_stall=int
While replaying I/O patterns using read_iolog the default
behavior attempts to respect timing information between I/Os.
Enabling replay_no_stall causes I/Os to be replayed as fast as
possible while still respecting ordering.
replay_redirect=str
While replaying I/O patterns using read_iolog the default
behavior is to replay the IOPS onto the major/minor device that
each IOP was recorded from. Setting replay_redirect causes all
IOPS to be replayed onto the single specified device regardless
of the device it was recorded from.
write_bw_log=str
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 write_log_log for
behaviour of given filename. For this option, the postfix is
_bw.log.
write_lat_log=str
Same as write_bw_log, 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.
disable_lat=bool
Disable measurements of total 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.
disable_clat=bool
Disable measurements of completion latency numbers. See
disable_lat.
disable_slat=bool
Disable measurements of submission latency numbers. See
disable_lat.
disable_bw_measurement=bool
Disable measurements of throughput/bandwidth numbers. See
disable_lat.
lockmem=int
Pin the specified amount of memory with mlock(2). Can be used
to simulate a smaller amount of memory.
exec_prerun=str
Before running the job, execute the specified command with
system(3).
exec_postrun=str
Same as exec_prerun, but the command is executed after the job
completes.
ioscheduler=str
Attempt to switch the device hosting the file to the specified
I/O scheduler.
cpuload=int
If the job is a CPU cycle-eater, attempt to use the specified
percentage of CPU cycles.
cpuchunks=int
If the job is a CPU cycle-eater, split the load into cycles of
the given time in milliseconds.
disk_util=bool
Generate disk utilization statistics if the platform supports
it. Default: true.
gtod_reduce=bool
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.
gtod_cpu=int
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.
cgroup=str
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
cgroup_weight=int
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.
cgroup_nodelete=bool
Normally fio will delete the cgroups it has created after the
job completion. To override this behavior and to leave cgroups
around after the job completion, set cgroup_nodelete=1. This can
be useful if one wants to inspect various cgroup files after job
completion. Default: false
uid=int
Instead of running as the invoking user, set the user ID to this
value before the thread/process does any work.
gid=int
Set group ID, see uid.
clat_percentiles=bool
Enable the reporting of percentiles of completion latencies.
percentile_list=float_list
Overwrite the default list of percentiles for completion
latencies. Each number is a floating number in the range
(0,100], and the maximum length of the list is 20. Use ':' to
separate the numbers. For example, --percentile_list=99.5:99.9
will cause fio to report the values of completion latency below
which 99.5% and 99.9% of the observed latencies fell,
respectively.
OUTPUT
While running, fio will display the status of the created jobs. For
example:
Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta
00h:01m:31s]
The characters in the first set of brackets denote the current status
of each threads. The possible values are:
P Setup but not started.
C Thread created.
I Initialized, waiting.
R Running, doing sequential reads.
r Running, doing random reads.
W Running, doing sequential writes.
w Running, doing random writes.
M Running, doing mixed sequential reads/writes.
m Running, doing mixed random reads/writes.
F Running, currently waiting for fsync(2).
V Running, verifying written data.
E Exited, not reaped by main thread.
- Exited, thread reaped.
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.
When fio completes (or is interrupted by Ctrl-C), it will show data for
each thread, each group of threads, and each disk, in that order.
Per-thread statistics first show the threads client number, group-id,
and error code. The remaining figures are as follows:
io Number of megabytes of I/O performed.
bw Average data rate (bandwidth).
runt Threads run time.
slat Submission latency minimum, maximum, average and standard
deviation. This is the time it took to submit the I/O.
clat Completion latency minimum, maximum, average and standard
deviation. This is the time between submission and
completion.
bw Bandwidth minimum, maximum, percentage of aggregate
bandwidth received, average and standard deviation.
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.
IO depths
Distribution of I/O depths. Each depth includes
everything less than (or equal) to it, but greater than
the previous depth.
IO issued
Number of read/write requests issued, and number of short
read/write requests.
IO latencies
Distribution of I/O completion latencies. The numbers
follow the same pattern as IO depths.
The group statistics show:
io Number of megabytes I/O performed.
aggrb Aggregate bandwidth of threads in the group.
minb Minimum average bandwidth a thread saw.
maxb Maximum average bandwidth a thread saw.
mint Shortest runtime of threads in the group.
maxt Longest runtime of threads in the group.
Finally, disk statistics are printed with reads first:
ios Number of I/Os performed by all groups.
merge Number of merges in the I/O scheduler.
ticks Number of ticks we kept the disk busy.
io_queue
Total time spent in the disk queue.
util Disk utilization.
TERSE OUTPUT
If the --minimal option is given, the results will be printed in a
semicolon-delimited format suitable for scripted use - a job
description (if provided) follows on a new line. Note that the first
number in the line is the version number. If the output has to be
changed for some reason, this number will be incremented by 1 to
signify that change. The fields are:
version, jobname, groupid, error
Read status:
Total I/O (KB), bandwidth (KB/s), runtime (ms)
Submission latency:
min, max, mean, standard deviation
Completion latency:
min, max, mean, standard deviation
Total latency:
min, max, mean, standard deviation
Bandwidth:
min, max, aggregate percentage of total, mean,
standard deviation
Write status:
Total I/O (KB), bandwidth (KB/s), runtime (ms)
Submission latency:
min, max, mean, standard deviation
Completion latency:
min, max, mean, standard deviation
Total latency:
min, max, mean, standard deviation
Bandwidth:
min, max, aggregate percentage of total, mean,
standard deviation
CPU usage:
user, system, context switches, major page faults, minor
page faults
IO depth distribution:
<=1, 2, 4, 8, 16, 32, >=64
IO latency distribution:
Microseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
Milliseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000,
2000, >=2000
Error Info (dependent on continue_on_error, default off):
total # errors, first error code
text description (if provided in config - appears on newline)
AUTHORS
fio was written by Jens Axboe <[email protected]>, now Jens Axboe <[email protected]>. This man page was written by Aaron Carroll <[email protected]> based on documentation by Jens Axboe.
REPORTING BUGS
Report bugs to the fio mailing list <[email protected]>. See README.
SEE ALSO
For further documentation see HOWTO and README.
Sample jobfiles are available in the examples directory.