.TP
.BI offset \fR=\fPint
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 \fBblockalign\fR\-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 \fBblocksize\fR or to the value of \fBoffset_align\fR 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
\fBsize\fR 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%.
.TP
+.BI offset_align \fR=\fPint
+If set to non-zero value, the byte offset generated by a percentage \fBoffset\fR
+is aligned upwards to this value. Defaults to 0 meaning that a percentage
+offset is aligned to the minimum block size.
+.TP
.BI offset_increment \fR=\fPint
If this is provided, then the real offset becomes `\fBoffset\fR + \fBoffset_increment\fR
* thread_number', where the thread number is a counter that starts at 0 and
mix of random data and a fixed pattern. The fixed pattern is either zeros,
or the pattern specified by \fBbuffer_pattern\fR. 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 \fBrefill_buffers\fR.
+block size unit, see \fBbuffer_compress_chunk\fR for setting a finer granularity
+of compressible regions.
.TP
.BI buffer_compress_chunk \fR=\fPint
See \fBbuffer_compress_percentage\fR. This setting allows fio to manage
will provide \fBbuffer_compress_percentage\fR 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. Defaults to 512.
.TP
.BI buffer_pattern \fR=\fPstr
If set, fio will fill the I/O buffers with this pattern or with the contents
details of writing an external I/O engine.
.TP
.B filecreate
-Create empty files only. \fBfilesize\fR still needs to be specified so that fio
-will run and grab latency results, but no IO will actually be done on the files.
+Simply create the files and do no I/O to them. You still need to set
+\fBfilesize\fR so that all the accounting still occurs, but no actual I/O will be
+done other than creating the file.
.SS "I/O engine specific parameters"
In addition, there are some parameters which are only valid when a specific
\fBioengine\fR is in use. These are used identically to normal parameters,
.TP
.BI write_bw_log \fR=\fPstr
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
-\fBfio_generate_plots\fR script uses gnuplot to turn these
-text files into nice graphs. See \fBwrite_lat_log\fR for behavior of
-given filename. For this option, the postfix is `_bw.x.log', where `x'
-is the index of the job (1..N, where N is the number of jobs). If
-\fBper_job_logs\fR is false, then the filename will not include the job
-index. See \fBLOG FILE FORMATS\fR section.
-.TP
-.BI write_lat_log \fR=\fPstr
-Same as \fBwrite_bw_log\fR, 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 `jobname_type.log' is
-used. Even if the filename is given, fio will still append the type of
-log. So if one specifies:
+the bandwidth of the jobs in their lifetime.
.RS
+.P
+If no str argument is given, the default filename of
+`jobname_type.x.log' is used. Even when the argument is given, fio
+will still append the type of log. So if one specifies:
.RS
.P
-write_lat_log=foo
+write_bw_log=foo
.RE
.P
-The actual log names will be `foo_slat.x.log', `foo_clat.x.log',
-and `foo_lat.x.log', where `x' is the index of the job (1..N, where N
-is the number of jobs). This helps \fBfio_generate_plots\fR find the
-logs automatically. If \fBper_job_logs\fR is false, then the filename
-will not include the job index. See \fBLOG FILE FORMATS\fR section.
+The actual log name will be `foo_bw.x.log' where `x' is the index
+of the job (1..N, where N is the number of jobs). If
+\fBper_job_logs\fR is false, then the filename will not include the
+`.x` job index.
+.P
+The included \fBfio_generate_plots\fR script uses gnuplot to turn these
+text files into nice graphs. See the \fBLOG FILE FORMATS\fR section for how data is
+structured within the file.
.RE
.TP
+.BI write_lat_log \fR=\fPstr
+Same as \fBwrite_bw_log\fR, except this option creates I/O
+submission (e.g., `name_slat.x.log'), completion (e.g.,
+`name_clat.x.log'), and total (e.g., `name_lat.x.log') latency
+files instead. See \fBwrite_bw_log\fR for details about the
+filename format and the \fBLOG FILE FORMATS\fR section for how data is structured
+within the files.
+.TP
.BI write_hist_log \fR=\fPstr
-Same as \fBwrite_lat_log\fR, but writes I/O completion latency
-histograms. If no filename is given with this option, the default filename
-of `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 \fBper_job_logs\fR is false,
-then the filename will not include the job index. See \fBLOG FILE FORMATS\fR section.
+Same as \fBwrite_bw_log\fR but writes an I/O completion latency
+histogram file (e.g., `name_hist.x.log') instead. Note that this
+file will be empty unless \fBlog_hist_msec\fR has also been set.
+See \fBwrite_bw_log\fR for details about the filename format and
+the \fBLOG FILE FORMATS\fR section for how data is structured
+within the file.
.TP
.BI write_iops_log \fR=\fPstr
-Same as \fBwrite_bw_log\fR, but writes IOPS. If no filename is given
-with this option, the default filename of `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 \fBper_job_logs\fR is false, then the filename will not include
-the job index. See \fBLOG FILE FORMATS\fR section.
+Same as \fBwrite_bw_log\fR, but writes an IOPS file (e.g.
+`name_iops.x.log') instead. See \fBwrite_bw_log\fR for
+details about the filename format and the \fBLOG FILE FORMATS\fR section for how data
+is structured within the file.
.TP
.BI log_avg_msec \fR=\fPint
By default, fio will log an entry in the iops, latency, or bw log for every
\fBlog_avg_msec\fR 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
-\fBlog_hist_coarseness\fR as well. Defaults to 0, meaning histogram
-logging is disabled.
+\fBlog_hist_coarseness\fR and \fBwrite_hist_log\fR as well.
+Defaults to 0, meaning histogram logging is disabled.
.TP
.BI log_hist_coarseness \fR=\fPint
Integer ranging from 0 to 6, defining the coarseness of the resolution of
mutually exclusive with \fBlat_percentiles\fR.
.TP
.BI lat_percentiles \fR=\fPbool
-Enable the reporting of percentiles of IO latencies. This is similar to
+Enable the reporting of percentiles of I/O latencies. This is similar to
\fBclat_percentiles\fR, except that this includes the submission latency.
This option is mutually exclusive with \fBclat_percentiles\fR.
.TP
.B I
Thread initialized, waiting or generating necessary data.
.TP
-.B P
+.B p
Thread running pre\-reading file(s).
.TP
.B /
short or dropped.
.TP
.B IO latency
-These values are for \fBlatency-target\fR and related options. When
+These values are for \fBlatency_target\fR and related options. When
these options are engaged, this section describes the I/O depth required
to meet the specified latency target.
.RE
projects / fio.git / blobdiff