Add total latency log

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index cafe1893656cfdff733c9b4368a92396ce9bd46c..7db02b1e5a6758a5930bde67e4b6d8a030364239 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -849,7 +849,7 @@ verify=str  If writing to a file, fio can verify the file contents
 
                        meta    Write extra information about each io
                                (timestamp, block number etc.). The block
-                               number is verified.
+                               number is verified. See also verify_pattern.
 
                        null    Only pretend to verify. Useful for testing
                                internals with ioengine=null, not for much
@@ -887,7 +887,8 @@ verify_pattern=str  If set, fio will fill the io buffers with this
                width of the pattern, fio will fill 1/2/3/4 bytes of the
                buffer at the time(it can be either a decimal or a hex number).
                The verify_pattern if larger than a 32-bit quantity has to
-               be a hex number that starts with either "0x" or "0X".
+               be a hex number that starts with either "0x" or "0X". Use
+               with verify=meta.
 
 verify_fatal=bool      Normally fio will keep checking the entire contents
                before quitting on a block verification failure. If this
@@ -975,15 +976,16 @@ write_bw_log=str If given, write a bandwidth log of the jobs in this job
                filename. For this option, the postfix is _bw.log.
 
 write_lat_log=str Same as write_bw_log, except that this option stores io
-               completion 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
+               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
 
                write_lat_log=foo
 
-               The actual log names will be foo_clat.log and foo_slat.log.
-               This helps fio_generate_plot fine the logs automatically.
+               The actual log names will be foo_slat.log, foo_slat.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
@@ -1007,18 +1009,21 @@ cpuchunks=int   If the job is a CPU cycle eater, split the load into
 disk_util=bool Generate disk utilization statistics, if the platform
                supports it. Defaults to on.
 
-disable_clat=bool Disable measurements of completion latency numbers. Useful
+disable_lat=bool Disable measurements of total latency numbers. Useful
                only for cutting back the number of calls to gettimeofday,
                as that does impact performance at really high IOPS rates.
                Note that to really get rid of a large amount of these
                calls, this option must be used with disable_slat and
                disable_bw as well.
 
+disable_clat=bool Disable measurements of completion latency numbers. See
+               disable_lat.
+
 disable_slat=bool Disable measurements of submission latency numbers. See
-               disable_clat.
+               disable_slat.
 
 disable_bw=bool        Disable measurements of throughput/bandwidth numbers. See
-               disable_clat.
+               disable_lat.
 
 gtod_reduce=bool Enable all of the gettimeofday() reducing options
                (disable_clat, disable_slat, disable_bw) plus reduce