IO engine How do we issue io? We could be memory mapping the
file, we could be using regular read/write, we
- could be using splice, async io, or even
+ could be using splice, async io, syslet, or even
SG (SCSI generic sg).
IO depth If the io engine is async, how large a queuing
A global section sets defaults for the jobs described in that file. A job
may override a global section parameter, and a job file may even have
several global sections if so desired. A job is only affected by a global
-section residing above it. If the first character in a line is a ';', the
-entire line is discarded as a comment.
+section residing above it. If the first character in a line is a ';' or a
+'#', the entire line is discarded as a comment.
So lets look at a really simple job file that define to threads, each
randomly reading from a 128MiB file.
special purpose of also signaling the start of a new
job.
+description=str Text description of the job. Doesn't do anything except
+ dump this text description when this job is run. It's
+ not parsed.
+
directory=str Prefix filenames with this directory. Used to places files
in a different location than "./".
filename=str Fio normally makes up a filename 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.
+ a filename for each of them to override the default. If
+ the ioengine used is 'net', the filename is the host and
+ port to connect to in the format of =host:port.
rw=str Type of io pattern. Accepted values are:
vmsplice(2) to transfer data from user
space to the kernel.
+ syslet-rw Use the syslet system calls to make
+ regular read/write async.
+
sg SCSI generic sg v3 io. May either be
synchronous using the SG_IO ioctl, or if
the target is an sg character device
to. This is mainly used to exercise fio
itself and for debugging/testing purposes.
+ net Transfer over the network to given host:port.
+ 'filename' must be set appropriately to
+ filename=host:port regardless of send
+ or receive, if the latter only the port
+ argument is used.
+
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
concurrency.
+iodepth_low=int The low water mark indicating when to start filling
+ the queue again. Defaults to the same as iodepth, meaning
+ that fio will attempt to keep the queue full at all times.
+ If iodepth is set to eg 16 and iodepth_low is set to 4, then
+ after fio has filled the queue of 16 requests, it will let
+ the depth drain down to 4 before starting to fill it again.
+
direct=bool If value is true, use non-buffered io. This is usually
O_DIRECT.
thinktime=int Stall the job x microseconds after an io has completed before
issuing the next. May be used to simulate processing being
- done by an application. See thinktime_blocks.
+ done by an application. See thinktime_blocks and
+ thinktime_spin.
+
+thinktime_spin=int
+ Only valid if thinktime is set - pretend to spend CPU time
+ doing something with the data received, before falling back
+ to sleeping for the rest of the period specified by
+ thinktime.
thinktime_blocks
Only valid if thinktime is set - control how many blocks
create_fsync=bool fsync the data file after creation. This is the
default.
-unlink=bool Unlink the job files when done. fio defaults to doing this,
- if it created the file itself.
+unlink=bool Unlink the job files when done. Not the default, as repeated
+ runs of that job would then waste time recreating the fileset
+ again and again.
loops=int Run the specified number of iterations of this job. Used
to repeat the same workload a given number of times. Defaults
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%
+ 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%
The client number is printed, along with the group id and error of that
thread. Below is the io statistics, here for writes. In the order listed,
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 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,
+ meaning that 2=1.6% means that 1.6% of the IO completed
+ within 2 msecs, 20=12.8% means that 12.8% of the IO
+ took more than 10 msecs, but less than (or equal to) 20 msecs.
After each client has been listed, the group statistics are printed. They
will look like this:
projects / fio.git / blobdiff