Fio defaults to read if the option is not specified.
For mixed I/O, the default split is 50/50. For certain types of io the result
may still be skewed a bit, since the speed may be different. It is possible to
-specify a number of IO's to do before getting a new offset, this is done by
+specify a number of IOs to do before getting a new offset, this is done by
appending a `:\fI<nr>\fR to the end of the string given. For a random read, it
would look like \fBrw=randread:8\fR for passing in an offset modifier with a
value of 8. If the postfix is used with a sequential IO pattern, then the value
.P
\fBsequential\fR is only useful for random IO, where fio would normally
generate a new random offset for every IO. If you append eg 8 to randread, you
-would get a new random offset for every 8 IO's. The result would be a seek for
-only every 8 IO's, instead of for every IO. Use \fBrw=randread:8\fR to specify
+would get a new random offset for every 8 IOs. The result would be a seek for
+only every 8 IOs, instead of for every IO. Use \fBrw=randread:8\fR to specify
that. As sequential IO is already sequential, setting \fBsequential\fR for that
would not result in any differences. \fBidentical\fR behaves in a similar
fashion, except it sends the same offset 8 number of times before generating a
.TP
.BI log_offset \fR=\fPbool
If this is set, the iolog options will include the byte offset for the IO
-entry as well as the other data values.
+entry as well as the other data values. Defaults to 0 meaning that offsets are
+not present in logs. See the \fBLOG FILE FORMATS\fR section.
.TP
.BI log_compression \fR=\fPint
If this is set, fio will compress the IO logs as it goes, to keep the memory
Set RWF_HIPRI on IO, indicating to the kernel that it's of
higher priority than normal.
.TP
+.BI (pvsync2)hipri_percentage
+When hipri is set this determines the probability of a pvsync2 IO being high
+priority. The default is 100%.
+.TP
.BI (net,netsplice)hostname \fR=\fPstr
The host name or IP address to use for TCP or UDP based IO.
If the job is a TCP listener or UDP reader, the hostname is not
Number of I/Os performed by all groups.
.TP
.B merge
-Number of merges in the I/O scheduler.
+Number of merges performed by the I/O scheduler.
.TP
.B ticks
Number of ticks we kept the disk busy.
terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_max;read_clat_min;read_clat_mean;read_clat_dev;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_max;write_clat_min;write_clat_mean;write_clat_dev;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;cpu_user;cpu_sys;cpu_csw;cpu_mjf;pu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
.fi
.RE
+.SH JSON+ OUTPUT
+The \fBjson+\fR output format is identical to the \fBjson\fR output format except that it
+adds a full dump of the completion latency bins. Each \fBbins\fR object contains a
+set of (key, value) pairs where keys are latency durations and values count how
+many I/Os had completion latencies of the corresponding duration. For example,
+consider:
+
+.RS
+"bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
+.RE
+
+This data indicates that one I/O required 87,552ns to complete, two I/Os required
+100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
+
+Also included with fio is a Python script \fBfio_jsonplus_clat2csv\fR that takes
+json+ output and generates CSV-formatted latency data suitable for plotting.
+
+The latency durations actually represent the midpoints of latency intervals.
+For details refer to stat.h.
+
+
.SH TRACE FILE FORMAT
There are two trace file format that you can encounter. The older (v1) format
is unsupported since version 1.20-rc3 (March 2008). It will still be described
Fio supports a variety of log file formats, for logging latencies, bandwidth,
and IOPS. The logs share a common format, which looks like this:
-.B time (msec), value, data direction, offset
+.B time (msec), value, data direction, block size (bytes), offset (bytes)
Time for the log entry is always in milliseconds. The value logged depends
on the type of log, it will be one of the following:
.PD
.P
-The \fIoffset\fR is the offset, in bytes, from the start of the file, for that
-particular IO. The logging of the offset can be toggled with \fBlog_offset\fR.
+The entry's *block size* is always in bytes. The \fIoffset\fR is the offset, in
+bytes, from the start of the file, for that particular IO. The logging of the
+offset can be toggled with \fBlog_offset\fR.
If windowed logging is enabled through \fBlog_avg_msec\fR, then fio doesn't log
individual IOs. Instead of logs the average values over the specified
-period of time. Since \fIdata direction\fR and \fIoffset\fR are per-IO values,
-they aren't applicable if windowed logging is enabled. If windowed logging
-is enabled and \fBlog_max_value\fR is set, then fio logs maximum values in
-that window instead of averages.
+period of time. Since \fIdata direction\fR, \fIblock size\fR and \fIoffset\fR
+are per-IO values, if windowed logging is enabled they aren't applicable and
+will be 0. If windowed logging is enabled and \fBlog_max_value\fR is set, then
+fio logs maximum values in that window instead of averages.
For histogram logging the logs look like this:
projects / fio.git / blobdiff