could be using splice, async io, or even
SG (SCSI generic sg).
- IO depth If the io engine is async, how large a queueing
+ IO depth If the io engine is async, how large a queuing
depth do we want to maintain?
IO type Should we be doing buffered io, or direct/raw io?
of those files. Internally that is the same as using the 'stonewall'
parameter described the the parameter section.
+If the job file contains only one job, you may as well just give the
+parameters on the command line. The command line parameters are identical
+to the job parameters, with a few extra that control global parameters
+(see README). For example, for the job file parameter iodepth=2, the
+mirror command line option would be --iodepth 2 or --iodepth=2. You can
+also use the command line for giving more than one job entry. For each
+--name option that fio sees, it will start a new job with that name.
+Command line entries following a --name entry will apply to that job,
+until there are no more entries or a new --name entry is seen. This is
+similar to the job file options, where each option applies to the current
+job until a new [] job entry is seen.
+
fio does not need to run as root, except if the files or devices specified
in the job section requires that. Some other options may also be restricted,
-such as memory locking, io scheduler switching, and descreasing the nice value.
+such as memory locking, io scheduler switching, and decreasing the nice value.
4.0 Job file format
As you can see, the job file sections themselves are empty as all the
described parameters are shared. As no filename= option is given, fio
-makes up a filename for each of the jobs as it sees fit.
+makes up a filename for each of the jobs as it sees fit. On the command
+line, this job would look as follows:
+
+$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
+
Lets look at an example that have a number of processes writing randomly
to files.
We want to use async io here, with a depth of 4 for each file. We also
increased the buffer size used to 32KiB and define numjobs to 4 to
fork 4 identical jobs. The result is 4 processes each randomly writing
-to their own 64MiB file.
+to their own 64MiB file. Instead of using the above job file, you could
+have given the parameters on the command line. For this case, you would
+specify:
+
+$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
fio ships with a few example job files, you can also look there for
inspiration.
int Integer. A whole number value, may be negative.
siint SI integer. A whole number value, which may contain a postfix
describing the base of the number. Accepted postfixes are k/m/g,
- meaning kilo, mega, and giga. So if you want to specifiy 4096,
+ meaning kilo, mega, and giga. So if you want to specify 4096,
you could either write out '4096' or just give 4k. The postfixes
signify base 2 values, so 1024 is 1k and 1024k is 1m and so on.
bool Boolean. Usually parsed as an integer, however only defined for
name=str ASCII name of the job. This may be used to override the
name printed by fio for this job. Otherwise the job
- name is used.
+ name is used. On the command line this parameter has the
+ special purpose of also signaling the start of a new
+ job.
directory=str Prefix filenames with this directory. Used to places files
in a different location than "./".
size if larger than the current file size. If this parameter
is not given and the file exists, the file size will be used.
-bs=siint The block size used for the io units. Defaults to 4k.
+bs=siint The block size used for the io units. Defaults to 4k. Values
+ can be given for both read and writes. If a single siint is
+ given, it will apply to both. If a second siint is specified
+ after a comma, it will apply to writes only. In other words,
+ the format is either bs=read_and_write or bs=read,write.
+ bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
+ for writes. If you only wish to set the write size, you
+ can do so by passing an empty read size - bs=,8k will set
+ 8k for writes and leave the read default value.
bsrange=irange Instead of giving a single block size, specify a range
and fio will mix the issued io block sizes. The issued
io unit will always be a multiple of the minimum value
- given.
+ given (also see bs_unaligned). Applies to both reads and
+ writes, however a second range can be given after a comma.
+ See bs=.
+
+bs_unaligned If this option is given, any byte size value within bsrange
+ may be used as a block range. This typically wont work with
+ direct IO, as that normally requires sector alignment.
nrfiles=int Number of files to use for this job. Defaults to 1.
space to the kernel.
sg SCSI generic sg v3 io. May either be
- syncrhonous using the SG_IO ioctl, or if
+ synchronous using the SG_IO ioctl, or if
the target is an sg character device
we use read(2) and write(2) for asynchronous
io.
+ null Doesn't transfer any data, just pretends
+ to. This is mainly used to exercise fio
+ itself and for debugging/testing purposes.
+
iodepth=int This defines how many io units to keep in flight against
the file. The default is 1 for each file defined in this
job, can be overridden with a larger value for higher
32 as a parameter, fio will sync the file for every 32
writes issued. If fio is using non-buffered io, we may
not sync the file. The exception is the sg io engine, which
- syncronizes the disk cache anyway.
+ synchronizes the disk cache anyway.
overwrite=bool If writing to a file, setup the file first and do overwrites.
end_fsync=bool If true, fsync file contents when the job exits.
-rwmixcycle=int Value in miliseconds describing how often to switch between
+rwmixcycle=int Value in milliseconds describing how often to switch between
reads and writes for a mixed workload. The default is
500 msecs.
up to 100%, the latter of the two will be used to override
the first.
+norandommap Normally fio will cover every block of the file when doing
+ random IO. If this option is given, fio will just get a
+ new random offset without looking at past io history. This
+ means that some blocks may not be read or written, and that
+ some blocks may be read/written more than once. This option
+ is mutually exclusive with verify= for that reason.
+
nice=int Run the job with the given nice value. See man nice(2).
prio=int Set the io priority value of this job. Linux limits us to
bandwidth.
ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number
- of miliseconds.
+ of milliseconds.
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
desired action.
bwavgtime=int Average the calculated bandwidth over the given time. Value
- is specified in miliseconds.
+ is specified in milliseconds.
create_serialize=bool If true, serialize the file creating for the jobs.
This may be handy to avoid interleaving of data
crc32 Use a crc32 sum of the data area and store
it in the header of each block.
- This option can be used for repeated burnin tests of a
+ 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.
been read. The two zone options can be used to only do
io on zones of a file.
-write_iolog=str Write the issued io patterns to the specified file. See iolog.
+write_iolog=str Write the issued io patterns to the specified file. See
+ read_iolog.
-iolog=str Open an iolog with the specified file name and replay the
+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.
percentage of CPU cycles.
cpuchunks=int If the job is a CPU cycle eater, split the load into
- cycles of the given time. In miliseconds.
+ cycles of the given time. In milliseconds.
6.0 Interpreting the output
fio spits out a lot of output. While running, fio will display the
status of the jobs created. An example of that would be:
-Threads running: 1: [_r] [24.79% done] [eta 00h:01m:31s]
+Threads running: 1: [_r] [24.79% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
The characters inside the square brackets denote the current status of
each thread. The possible values (in typical life cycle order) are:
_ Thread reaped.
The other values are fairly self explanatory - number of threads
-currently running and doing io, and the estimated completion percentage
-and time for the running group. It's impossible to estimate runtime
-of the following groups (if any).
+currently running and doing io, rate of io since last check, and the estimated
+completion percentage and time for the running group. It's impossible to
+estimate runtime of the following groups (if any).
When fio is done (or interrupted by ctrl-c), it will show the data for
each thread, group of threads, and disks in that order. For each data
----------------
For scripted usage where you typically want to generate tables or graphs
-of the results, fio can output the results in a comma seperated format.
+of the results, fio can output the results in a comma separated format.
The format is one long line of values, such as:
client1,0,0,936,331,2894,0,0,0.000000,0.000000,1,170,22.115385,34.290410,16,714,84.252874%,366.500000,566.417819,3496,1237,2894,0,0,0.000000,0.000000,0,246,6.671625,21.436952,0,2534,55.465300%,1406.600000,2008.044216,0.000000%,0.431928%,1109
KiB IO, bandwidth (KiB/sec), runtime (msec)
Submission latency: min, max, mean, deviation
Completion latency: min, max, mean, deviation
- Bw: min, max, aggreate percentage of total, mean, deviation
+ Bw: min, max, aggregate percentage of total, mean, deviation
WRITE status:
KiB IO, bandwidth (KiB/sec), runtime (msec)
Submission latency: min, max, mean, deviation
Completion latency: min, max, mean, deviation
- Bw: min, max, aggreate percentage of total, mean, deviation
+ Bw: min, max, aggregate percentage of total, mean, deviation
CPU usage: user, system, context switches
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