Update documentation for random_distribution=gauss

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 482d69651c0362c3afd5863512dc32f7d73f3733..d70c9afebf04b9f0a2114e838dc340db3eeccf03 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -10,6 +10,7 @@ Table of contents
 7. Terse output
 8. Trace file format
 9. CPU idleness profiling
+10. Verification and triggers
 
 1.0 Overview and history
 ------------------------
@@ -305,6 +306,16 @@ name=str   ASCII name of the job. This may be used to override the
                special purpose of also signaling the start of a new
                job.
 
+wait_for=str   Specifies the name of the already defined job to wait
+               for. Single waitee name only may be specified. If set, the job
+               won't be started until all workers of the waitee job are done.
+
+               Wait_for operates on the job name basis, so there are a few
+               limitations. First, the waitee must be defined prior to the
+               waiter job (meaning no forward references). Second, if a job
+               is being referenced as a waitee, it must have a unique name
+               (no duplicate waitees).
+
 description=str        Text description of the job. Doesn't do anything except
                dump this text description when this job is run. It's
                not parsed.
@@ -952,6 +963,7 @@ random_distribution=str:float       By default, fio will use a completely uniform
                random          Uniform random distribution
                zipf            Zipf distribution
                pareto          Pareto distribution
+               gauss           Normal (guassian) distribution
 
                When using a zipf or pareto distribution, an input value
                is also needed to define the access pattern. For zipf, this
@@ -960,7 +972,9 @@ random_distribution=str:float       By default, fio will use a completely uniform
                what the given input values will yield in terms of hit rates.
                If you wanted to use zipf with a theta of 1.2, you would use
                random_distribution=zipf:1.2 as the option. If a non-uniform
-               model is used, fio will disable use of the random map.
+               model is used, fio will disable use of the random map. For
+               the gauss distribution, a normal deviation is supplied as
+               a value between 0 and 100.
 
 percentage_random=int  For a random workload, set how big a percentage should
                be random. This defaults to 100%, in which case the workload
@@ -1003,7 +1017,9 @@ random_generator=str      Fio supports the following engines for generating
                typically good enough. LFSR only works with single
                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.
+               some blocks multiple times. The default value is tausworthe,
+               unless the required space exceeds 2^32 blocks. If it does,
+               then tausworthe64 is selected automatically.
 
 nice=int       Run the job with the given nice value. See man nice(2).
 
@@ -1558,8 +1574,12 @@ log_avg_msec=int By default, fio will log an entry in the iops, latency,
                disk log, that can quickly grow to a very large size. Setting
                this option makes fio average the each log entry over the
                specified period of time, reducing the resolution of the log.
-               Defaults to 0.
+               See log_max as well. Defaults to 0, logging all entries.
 
+log_max=bool   If log_avg_msec is set, fio logs the average over that window.
+               If you instead want to log the maximum value, set this option
+               to 1. Defaults to 0, meaning that averaged values are logged.
+.
 log_offset=int If this is set, the iolog options will include the byte
                offset for the IO entry as well as the other data values.
 
@@ -1767,6 +1787,9 @@ that defines them is selected.
                enabled when polling for a minimum of 0 events (eg when
                iodepth_batch_complete=0).
 
+[psyncv2] hipri                Set RWF_HIPRI on IO, indicating to the kernel that
+                       it's of higher priority than normal.
+
 [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles.
 
 [cpu] cpuchunks=int Split the load into cycles of the given time. In
@@ -2203,7 +2226,7 @@ localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reb
 For this case, fio would wait for the server to send us the write state,
 then execute 'ipmi-reboot server' when that happened.
 
-10.1 Loading verify state
+10.2 Loading verify state
 -------------------------
 To load store write state, read verification job file must contain
 the verify_state_load option. If that is set, fio will load the previously