ioengine is file based, you can specify a number of files
by seperating 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
+ 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 direction set.
opendir=str Tell fio to recursively add any file it can find in this
directory and down the file system tree.
For the mixed io types, the default is to split them 50/50.
For certain types of io the result may still be skewed a bit,
- since the speed may be different.
+ 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 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.
randrepeat=bool For random IO workloads, seed the generator in a predictable
way so that results are repeatable across repetitions.
+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
+ kernel about it, in which case you can disable this option.
+ If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
+ IO and POSIX_FADV_RANDOM for random IO.
+
size=siint The total size of file io for this job. This may describe
the size of the single file the job uses, or it may be
divided between the number of files in the job. If the
may be used as a block range. This typically wont work with
direct IO, as that normally requires sector alignment.
+zero_buffers If this option is given, fio will init the IO buffers to
+ all zeroes. The default is to fill them with random data.
+
nrfiles=int Number of files to use for this job. Defaults to 1.
openfiles=int Number of files to keep open at the same time. Defaults to
will cause that job to do nothing but burn
85% of the CPU.
+ guasi The GUASI IO engine is the Generic Userspace
+ Asyncronous Syscall Interface approach
+ to async IO. See
+
+ http://www.xmailserver.org/guasi-lib.html
+
+ for more info on GUASI.
+
external Prefix to specify loading an external
IO engine object file. Append the engine
filename, eg ioengine=external:/tmp/foo.o
cpumask=int Set the CPU affinity of this job. The parameter given is a
bitmask of allowed CPU's the job may run on. See man
- sched_setaffinity(2).
+ sched_setaffinity(2). This may not work on all supported
+ operating systems or kernel versions.
startdelay=int Start this job the specified number of seconds after fio
has started. Only useful if the job file contains several
a specified job will run, so this parameter is handy to
cap the total runtime to a given time.
+time_based If set, fio will run for the duration of the runtime
+ specified even if the file(s) are completey read or
+ written. It will simply loop over the same workload
+ as many times as the runtime allows.
+
invalidate=bool Invalidate the buffer/page cache parts for this file prior
to starting io. Defaults to true.
crc32 Use a crc32 sum of the data area and store
it in the header of each block.
+ null Only pretend to verify. Useful for testing
+ internals with ioengine=null, not for much
+ else.
+
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.
+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
+ often the case when overwriting an existing file, since
+ the blocks are already laid out in the file system. You
+ can ignore this option unless doing huge amounts of really
+ fast IO where the red-black tree sorting CPU time becomes
+ significant.
+
stonewall Wait for preceeding jobs in the job file to exit, before
starting this one. Can be used to insert serialization
- points in the job file.
+ points in the job file. A stone wall also implies starting
+ a new reporting group.
+
+new_group Start a new reporting group. If this option isn't given,
+ jobs in a file will be part of the same reporting group
+ unless seperated by a stone wall (or if it's a group
+ by itself, with the numjobs option).
numjobs=int Create the specified number of clones of this job. May be
used to setup a larger number of threads/processes doing
read_iolog=str Open an iolog with the specified file name and replay the
io patterns it contains. This can be used to store a
- workload and replay it sometime later.
+ workload and replay it sometime later. The iolog given
+ may also be a blktrace binary file, which allows fio
+ 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).
write_bw_log If given, write a bandwidth log of the jobs in this job
file. Can be used to store data of the bandwidth of the
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. Defaults to on.
+
6.0 Interpreting the output
---------------------------
bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
cpu : usr=1.49%, sys=0.25%, ctx=7969
IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
+ issued r/w: total=0/32768, short=0/0
lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
io= Number of megabytes io performed
bw= Average bandwidth rate
runt= The runtime of that thread
- slat= Submission latency (avg being the average, dev being the
+ slat= Submission latency (avg being the average, stdev being the
standard deviation). This is the time it took to submit
the io. For sync io, the slat is really the completion
latency, since queue/complete is one operation there.
16= entries includes depths up to that value but higher
than the previous entry. In other words, it covers the
range from 16 to 31.
+IO issued= The number of read/write requests issued, and how many
+ of them were short.
IO latencies= The distribution of IO completion latencies. This is the
time from when IO leaves fio and when it gets completed.
The numbers follow the same pattern as the IO depths,
projects / fio.git / blobdiff