$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
+4.1 Environment variables
+-------------------------
+
fio also supports environment variable expansion in job files. Any
substring of the form "${VARNAME}" as part of an option value (in other
words, on the right of the `='), will be expanded to the value of the
fio ships with a few example job files, you can also look there for
inspiration.
+4.2 Reserved keywords
+---------------------
+
+Additionally, fio has a set of reserved keywords that will be replaced
+internally with the appropriate value. Those keywords are:
+
+$pagesize The architecture page size of the running system
+$mb_memory Megabytes of total memory in the system
+$ncpus Number of online available CPUs
+
+These can be used on the command line or in the job file, and will be
+automatically substituted with the current system values when the job
+is run. Simple math is also supported on these keywords, so you can
+perform actions like:
+
+size=8*$mb_memory
+
+and get that properly expanded to 8 times the size of memory in the
+machine.
+
5.0 Detailed list of parameters
-------------------------------
int SI integer. A whole number value, which may contain a suffix
describing the base of the number. Accepted suffixes are k/m/g/t/p,
meaning kilo, mega, giga, tera, and peta. The suffix is not case
- sensitive. So if you want to specify 4096, you could either write
+ sensitive, and you may also include trailing 'b' (eg 'kb' is the same
+ as 'k'). So if you want to specify 4096, you could either write
out '4096' or just give 4k. The suffixes signify base 2 values, so
- 1024 is 1k and 1024k is 1m and so on. If the option accepts an upper
- and lower range, use a colon ':' or minus '-' to separate such values.
- May also include a prefix to indicate numbers base. If 0x is used,
- the number is assumed to be hexadecimal. See irange.
+ 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly
+ set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the
+ case, then 1000 is used as the multiplier. This can be handy for
+ disks, since manufacturers generally use base 10 values when listing
+ the capacity of a drive. If the option accepts an upper and lower
+ range, use a colon ':' or minus '-' to separate such values. May also
+ include a prefix to indicate numbers base. If 0x is used, the number
+ is assumed to be hexadecimal. See irange.
bool Boolean. Usually parsed as an integer, however only defined for
true and false (1 and 0).
irange Integer range with suffix. Allows value range to be given, such
can specify a number of files by separating the names with a
':' colon. So if you wanted a job to open /dev/sda and /dev/sdb
as the two working files, you would use
- filename=/dev/sda:/dev/sdb. '-' is a reserved name, meaning
- stdin or stdout. Which of the two depends on the read/write
+ filename=/dev/sda:/dev/sdb. If the wanted filename does need to
+ include a colon, then escape that with a '\' character. For
+ instance, if the filename is "/dev/dsk/foo@3,0:c", then you would
+ use filename="/dev/dsk/foo@3,0\:c". '-' is a reserved name,
+ meaning stdin or stdout. Which of the two depends on the read/write
direction set.
opendir=str Tell fio to recursively add any file it can find in this
randrepeat=bool For random IO workloads, seed the generator in a predictable
way so that results are repeatable across repetitions.
+fallocate=bool 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.
+
fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
on what IO patterns it is likely to issue. Sometimes you
want to test specific IO patterns without telling the
limited by other options (such as 'runtime', for instance).
Unless specific nrfiles and filesize options are given,
fio will divide this size between the available files
- specified by the job.
+ specified by 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.
filesize=int Individual file sizes. May be a range, in which case fio
will select sizes for files at random within the given range
not sync the file. The exception is the sg io engine, which
synchronizes the disk cache anyway.
-fsyncdata=int Like fsync= but uses fdatasync() to only sync data and not
+fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
metadata blocks.
+ In FreeBSD there is no fdatasync(), this falls back to
+ using fsync()
+
+sync_file_range=str:val 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_WAIT_AFTER
+
+ 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 true, writes to a file will always overwrite existing
data. If the file doesn't already exist, it will be
it in the header of each block.
crc32c-intel Use hardware assisted crc32c calcuation
- provided on SSE4.2 enabled processors.
+ provided on SSE4.2 enabled processors. Falls
+ back to regular software crc32c, if not
+ supported by the system.
crc32 Use a crc32 sum of the data area and store
it in the header of each block.
sha256 Use sha256 as the checksum function.
+ sha1 Use optimized sha1 as the checksum function.
+
meta Write extra information about each io
(timestamp, block number etc.). The block
- number is verified.
+ number is verified. See also verify_pattern.
null Only pretend to verify. Useful for testing
internals with ioengine=null, not for much
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.
+ 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.
verifysort=bool If set, fio will sort written verify blocks when it deems
it faster to read them back in a sorted manner. This is
size of header_interval. blocksize should divide this
evenly.
-verify_pattern=int If set, fio will fill the io buffers with this
+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. The verify_pattern cannot be larger than
- a 32-bit quantity.
+ 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 Normally fio will keep checking the entire contents
before quitting on a block verification failure. If this
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 verify the previously written blocks before continuing
+ to write new ones.
+
+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).
stonewall Wait for preceeding jobs in the job file to exit, before
starting this one. Can be used to insert serialization
to replay a workload captured by blktrace. See blktrace
for how to capture such logging data. For blktrace replay,
the file needs to be turned into a blkparse binary data
- file first (blktrace <device> -d file_for_fio.bin).
+ file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
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
filename. For this option, the postfix is _bw.log.
write_lat_log=str Same as write_bw_log, except that this option stores io
- completion latencies instead. 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. So if one specifies
+ submission, completion, and total latencies instead. 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. So if one specifies
write_lat_log=foo
- The actual log names will be foo_clat.log and foo_slat.log.
- This helps fio_generate_plot fine the logs automatically.
+ The actual log names will be foo_slat.log, foo_slat.log,
+ and foo_lat.log. This helps fio_generate_plot fine the logs
+ automatically.
lockmem=int Pin down the specified amount of memory with mlock(2). Can
potentially be used instead of removing memory or booting
disk_util=bool Generate disk utilization statistics, if the platform
supports it. Defaults to on.
-disable_clat=bool Disable measurements of completion latency numbers. Useful
+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_clat.
+ disable_slat.
disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
- disable_clat.
+ disable_lat.
gtod_reduce=bool Enable all of the gettimeofday() reducing options
(disable_clat, disable_slat, disable_bw) plus reduce
for doing these time calls will be excluded from other
uses. Fio will manually clear it from the CPU mask of other
jobs.
+
continue_on_error=bool Normally fio will exit the job on the first observed
failure. If this option is set, fio will continue the job when
there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
given in the stats is the first error that was hit during the
run.
+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.
6.0 Interpreting the output
---------------------------
of the results, fio can output the results in a semicolon separated format.
The format is one long line of values, such as:
-client1;0;0;1906777;1090804;1790;0;0;0.000000;0.000000;0;0;0.000000;0.000000;929380;1152890;25.510151%;1078276.333333;128948.113404;0;0;0;0;0;0.000000;0.000000;0;0;0.000000;0.000000;0;0;0.000000%;0.000000;0.000000;100.000000%;0.000000%;324;100.0%;0.0%;0.0%;0.0%;0.0%;0.0%;0.0%;100.0%;0.0%;0.0%;0.0%;0.0%;0.0%
+2; client1;0;0;1906777;1090804;1790;0;0;0.000000;0.000000;0;0;0.000000;0.000000;929380;1152890;25.510151%;1078276.333333;128948.113404;0;0;0;0;0;0.000000;0.000000;0;0;0.000000;0.000000;0;0;0.000000%;0.000000;0.000000;100.000000%;0.000000%;324;100.0%;0.0%;0.0%;0.0%;0.0%;0.0%;0.0%;100.0%;0.0%;0.0%;0.0%;0.0%;0.0%
;0.0%;0.0%;0.0%;0.0%;0.0%
-To enable terse output, use the --minimal command line option.
+To enable terse output, use the --minimal command line option. The first
+value is the version of the terse output format. If the output has to
+be changed for some reason, this number will be incremented by 1 to
+signify that change.
Split up, the format is as follows:
- jobname, groupid, error
+ version, jobname, groupid, error
READ status:
KB IO, bandwidth (KB/sec), runtime (msec)
Submission latency: min, max, mean, deviation
Completion latency: min, max, mean, deviation
+ Total latency: min, max, mean, deviation
Bw: min, max, aggregate percentage of total, mean, deviation
WRITE status:
KB IO, bandwidth (KB/sec), runtime (msec)
Submission latency: min, max, mean, deviation
Completion latency: min, max, mean, deviation
+ Total latency: min, max, mean, deviation
Bw: min, max, aggregate percentage of total, mean, deviation
CPU usage: user, system, context switches, major faults, minor faults
IO depths: <=1, 2, 4, 8, 16, 32, >=64
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