.. option:: --max-jobs=nr
Set the maximum number of threads/processes to support to `nr`.
+ NOTE: On Linux, it may be necessary to increase the shared-memory
+ limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
+ creating jobs.
.. option:: --server=args
.. option:: --client=hostname
Instead of running the jobs locally, send and run them on the given `hostname`
- or set of `hostname`s. See `Client/Server`_ section.
+ or set of `hostname`\s. See `Client/Server`_ section.
.. option:: --remote-config=file
named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
will be used if no other format specifier is given.
+ If you specify a path then the directories will be created up to the
+ main directory for the file. So for example if you specify
+ ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
+ created before the file setup part of the job. If you specify
+ :option:`directory` then the path will be relative that directory,
+ otherwise it is treated as the absolute path.
+
.. option:: unique_filename=bool
To avoid collisions between networked clients, fio defaults to prefixing any
.. option:: offset=int
Start I/O at the provided offset in the file, given as either a fixed size in
- bytes or a percentage. If a percentage is given, the next ``blockalign``-ed
- offset will be used. Data before the given offset will not be touched. This
+ bytes or a percentage. If a percentage is given, the generated offset will be
+ aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
+ provided. Data before the given offset will not be touched. This
effectively caps the file size at `real_size - offset`. Can be combined with
:option:`size` to constrain the start and end range of the I/O workload.
A percentage can be specified by a number between 1 and 100 followed by '%',
for example, ``offset=20%`` to specify 20%.
+.. option:: offset_align=int
+
+ If set to non-zero value, the byte offset generated by a percentage ``offset``
+ is aligned upwards to this value. Defaults to 0 meaning that a percentage
+ offset is aligned to the minimum block size.
+
.. option:: offset_increment=int
If this is provided, then the real offset becomes `offset + offset_increment
mix of random data and a fixed pattern. The fixed pattern is either zeros,
or the pattern specified by :option:`buffer_pattern`. If the pattern option
is used, it might skew the compression ratio slightly. Note that this is per
- block size unit, for file/disk wide compression level that matches this
- setting, you'll also want to set :option:`refill_buffers`.
+ block size unit, see :option:`buffer_compress_chunk` for setting a finer
+ granularity of compression regions.
.. option:: buffer_compress_chunk=int
will provide :option:`buffer_compress_percentage` of blocksize random data,
followed by the remaining zeroed. With this set to some chunk size smaller
than the block size, fio can alternate random and zeroed data throughout the
- I/O buffer.
+ I/O buffer. This is particularly useful when bigger block sizes are used
+ for a job.
.. option:: buffer_pattern=str
Doesn't transfer any data, but burns CPU cycles according to the
:option:`cpuload` and :option:`cpuchunks` options. Setting
:option:`cpuload`\=85 will cause that job to do nothing but burn 85%
- of the CPU. In case of SMP machines, use :option:`numjobs`=<nr_of_cpu>
+ of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
to get desired CPU usage, as the cpuload only loads a
single CPU at the desired rate. A job never finishes unless there is
at least one non-cpuio job.
details of writing an external I/O engine.
**filecreate**
- Simply create the files and do no IO to them. You still need to
+ Simply create the files and do no I/O to them. You still need to
set `filesize` so that all the accounting still occurs, but no
- actual IO will be done other than creating the file.
+ actual I/O will be done other than creating the file.
I/O engine specific parameters
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
changing data and the overlapping region has a non-zero size. Setting
``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
serializing in-flight I/Os that have a non-zero overlap. Note that setting
- this option can reduce both performance and the `:option:iodepth` achieved.
+ this option can reduce both performance and the :option:`iodepth` achieved.
Additionally this option does not work when :option:`io_submit_mode` is set to
offload. Default: false.
.. option:: write_bw_log=str
If given, write a bandwidth log for this job. Can be used to store data of
- the bandwidth of the jobs in their lifetime. The included
- :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
- text files into nice graphs. See :option:`write_lat_log` for behavior of
- given filename. For this option, the postfix is :file:`_bw.x.log`, where `x`
- is the index of the job (`1..N`, where `N` is the number of jobs). If
- :option:`per_job_logs` is false, then the filename will not include the job
- index. See `Log File Formats`_.
+ the bandwidth of the jobs in their lifetime.
-.. option:: write_lat_log=str
+ If no str argument is given, the default filename of
+ :file:`jobname_type.x.log` is used. Even when the argument is given, fio
+ will still append the type of log. So if one specifies::
- Same as :option:`write_bw_log`, except that this option stores I/O
- submission, completion, and total latencies instead. If no filename is given
- with this option, the default filename of :file:`jobname_type.log` is
- used. Even if the filename is given, fio will still append the type of
- log. So if one specifies::
+ write_bw_log=foo
- write_lat_log=foo
+ The actual log name will be :file:`foo_bw.x.log` where `x` is the index
+ of the job (`1..N`, where `N` is the number of jobs). If
+ :option:`per_job_logs` is false, then the filename will not include the
+ `.x` job index.
+
+ The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
+ text files into nice graphs. See `Log File Formats`_ for how data is
+ structured within the file.
+
+.. option:: write_lat_log=str
- The actual log names will be :file:`foo_slat.x.log`, :file:`foo_clat.x.log`,
- and :file:`foo_lat.x.log`, where `x` is the index of the job (`1..N`, where `N`
- is the number of jobs). This helps :command:`fio_generate_plots` find the
- logs automatically. If :option:`per_job_logs` is false, then the filename
- will not include the job index. See `Log File Formats`_.
+ Same as :option:`write_bw_log`, except this option creates I/O
+ submission (e.g., `file:`name_slat.x.log`), completion (e.g.,
+ `file:`name_clat.x.log`), and total (e.g., `file:`name_lat.x.log`)
+ latency files instead. See :option:`write_bw_log` for details about
+ the filename format and `Log File Formats`_ for how data is structured
+ within the files.
.. option:: write_hist_log=str
- Same as :option:`write_lat_log`, but writes I/O completion latency
- histograms. If no filename is given with this option, the default filename
- of :file:`jobname_clat_hist.x.log` is used, where `x` is the index of the
- job (`1..N`, where `N` is the number of jobs). Even if the filename is given,
- fio will still append the type of log. If :option:`per_job_logs` is false,
- then the filename will not include the job index. See `Log File Formats`_.
+ Same as :option:`write_bw_log` but writes an I/O completion latency
+ histogram file (e.g., `file:`name_hist.x.log`) instead. Note that this
+ file will be empty unless :option:`log_hist_msec` has also been set.
+ See :option:`write_bw_log` for details about the filename format and
+ `Log File Formats`_ for how data is structured within the file.
.. option:: write_iops_log=str
- Same as :option:`write_bw_log`, but writes IOPS. If no filename is given
- with this option, the default filename of :file:`jobname_type.x.log` is
- used, where `x` is the index of the job (`1..N`, where `N` is the number of
- jobs). Even if the filename is given, fio will still append the type of
- log. If :option:`per_job_logs` is false, then the filename will not include
- the job index. See `Log File Formats`_.
+ Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
+ `file:`name_iops.x.log`) instead. See :option:`write_bw_log` for
+ details about the filename format and `Log File Formats`_ for how data
+ is structured within the file.
.. option:: log_avg_msec=int
:option:`log_avg_msec` is inaccurate. Setting this option makes fio log
histogram entries over the specified period of time, reducing log sizes for
high IOPS devices while retaining percentile accuracy. See
- :option:`log_hist_coarseness` as well. Defaults to 0, meaning histogram
- logging is disabled.
+ :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
+ Defaults to 0, meaning histogram logging is disabled.
.. option:: log_hist_coarseness=int
Integer ranging from 0 to 6, defining the coarseness of the resolution of
the histogram logs enabled with :option:`log_hist_msec`. For each increment
in coarseness, fio outputs half as many bins. Defaults to 0, for which
- histogram logs contain 1216 latency bins. See `Log File Formats`_.
+ histogram logs contain 1216 latency bins. See :option:`write_hist_log`
+ and `Log File Formats`_.
.. option:: log_max_value=bool
.. option:: lat_percentiles=bool
- Enable the reporting of percentiles of IO latencies. This is similar
+ Enable the reporting of percentiles of I/O latencies. This is similar
to :option:`clat_percentiles`, except that this includes the
submission latency. This option is mutually exclusive with
:option:`clat_percentiles`.
short or dropped.
**IO latency**
- These values are for `--latency-target` and related options. When
+ These values are for :option:`latency_target` and related options. When
these options are engaged, this section describes the I/O depth required
to meet the specified latency target.
projects / fio.git / blobdiff