6. Normal output
7. Terse output
8. Trace file format
+9. CPU idleness profiling
1.0 Overview and history
------------------------
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. On Windows, disk devices are accessed
- as \\.\PhysicalDrive0 for the first device, \\.\PhysicalDrive1
- for the second etc.
- Note: Windows and FreeBSD prevent write access to areas of the disk
- containing in-use data (e.g. filesystems).
- 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.
+ filename=/dev/sda:/dev/sdb. On Windows, disk devices are
+ accessed as \\.\PhysicalDrive0 for the first device,
+ \\.\PhysicalDrive1 for the second etc. Note: Windows and
+ FreeBSD prevent write access to areas of the disk containing
+ in-use data (e.g. filesystems).
+ 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.
+
+filename_format=str
+ If sharing multiple files between jobs, it is usually necessary
+ to have fio generate the exact names that you want. By default,
+ fio will name a file based on the default file format
+ specification of jobname.jobnumber.filenumber. With this
+ option, that can be customized. Fio will recognize and replace
+ the following keywords in this string:
+
+ $jobname
+ The name of the worker thread or process.
+
+ $jobnum
+ The incremental number of the worker thread or
+ process.
+
+ $filenum
+ The incremental number of the file for that worker
+ thread or process.
+
+ To have dependent jobs share a set of files, this option can
+ be set to have fio generate filenames that are shared between
+ the two. For instance, if testfiles.$filenum is specified,
+ file number 4 for any job will be named testfiles.4. The
+ default of $jobname.$jobnum.$filenum will be used if
+ no other format specifier is given.
opendir=str Tell fio to recursively add any file it can find in this
directory and down the file system tree.
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.
-
readwrite=str
rw=str Type of io pattern. Accepted values are:
ten unit instead, for obvious reasons. Allow values are
1024 or 1000, with 1024 being the default.
+unified_rw_reporting=bool Fio normally reports statistics on a per
+ data direction basis, meaning that read, write, and trim are
+ accounted and reported separately. If this option is set,
+ the fio will sum the results and report them as "mixed"
+ instead.
+
randrepeat=bool For random IO workloads, seed the generator in a predictable
way so that results are repeatable across repetitions.
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
+ 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.
random_distribution=zipf:1.2 as the option. If a non-uniform
model is used, fio will disable use of the random map.
+percentage_random=int For a random workload, set how big a percentage should
+ be random. This defaults to 100%, in which case the workload
+ is fully random. It can be set from anywhere from 0 to 100.
+ Setting it to 0 would make the workload fully sequential. Any
+ setting in between will result in a random mix of sequential
+ and random IO, at the given percentages.
+
+percentage_sequential=int See percentage_random. It is guaranteed that
+ they add up to 100. The later setting has priority, each
+ will adjust the other.
+
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
block sizes, not with workloads that use multiple block
sizes. If used with such a workload, fio may read or write
some blocks multiple times.
-
+
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
write_lat_log=foo
- The actual log names will be foo_slat.log, foo_slat.log,
+ The actual log names will be foo_slat.log, foo_clat.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
with less memory to simulate a smaller amount of memory.
+ The amount specified is per worker.
exec_prerun=str Before running this job, issue the command specified
through system(3).
[netsplice] port=int
[net] port=int The TCP or UDP port to bind to or connect to.
+[netsplice] nodelay=bool
+[net] nodelay=bool Set TCP_NODELAY on TCP connections.
+
[netsplice] protocol=str
[netsplice] proto=str
[net] protocol=str
It is also possible to get fio to dump the current output while it is
running, without terminating the job. To do that, send fio the USR1 signal.
+You can also get regularly timed dumps by using the --status-interval
+parameter, or by creating a file in /tmp named fio-dump-status. If fio
+sees this file, it will unlink it and dump the current output status.
7.0 Terse output
sync fsync() the file
datasync fdatasync() the file
trim trim the given file from the given 'offset' for 'length' bytes
+
+
+9.0 CPU idleness profiling
+--------------------------
+In some cases, we want to understand CPU overhead in a test. For example,
+we test patches for the specific goodness of whether they reduce CPU usage.
+fio implements a balloon approach to create a thread per CPU that runs at
+idle priority, meaning that it only runs when nobody else needs the cpu.
+By measuring the amount of work completed by the thread, idleness of each
+CPU can be derived accordingly.
+
+An unit work is defined as touching a full page of unsigned characters. Mean
+and standard deviation of time to complete an unit work is reported in "unit
+work" section. Options can be chosen to report detailed percpu idleness or
+overall system idleness by aggregating percpu stats.
projects / fio.git / blobdiff