[PATCH] Change timeout to runtime and rearrange option entries

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 6ac744cd3d436124f8474ff135c7a842fb92136b..57c0730b13d0ef7ef8b257a97ff56c1181aa53cf 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -211,6 +211,9 @@ rw=str              Type of io pattern. Accepted values are:
                For certain types of io the result may still be skewed a bit,
                since the speed may be different.
 
+randrepeat=bool        For random IO workloads, seed the generator in a predictable
+               way so that results are repeatable across repetitions.
+
 size=siint     The total size of file io for this job. This may describe
                the size of the single file the job uses, or it may be
                divided between the number of files in the job. If the
@@ -319,7 +322,13 @@ prioclass=int      Set the io priority class. See man ionice(1).
 
 thinktime=int  Stall the job x microseconds after an io has completed before
                issuing the next. May be used to simulate processing being
-               done by an application.
+               done by an application. See thinktime_blocks.
+
+thinktime_blocks
+               Only valid if thinktime is set - control how many blocks
+               to issue, before waiting 'thinktime' usecs. If not set,
+               defaults to 1 which will make fio wait 'thinktime' usecs
+               after every block.
 
 rate=int       Cap the bandwidth used by this job to this number of KiB/sec.
 
@@ -338,7 +347,7 @@ startdelay=int      Start this job the specified number of seconds after fio
                jobs, and you want to delay starting some jobs to a certain
                time.
 
-timeout=int    Tell fio to terminate processing after the specified number
+runtime=int    Tell fio to terminate processing after the specified number
                of seconds. It can be quite hard to determine for how long
                a specified job will run, so this parameter is handy to
                cap the total runtime to a given time.
@@ -359,11 +368,39 @@ mem=str           Fio can use various types of memory as the io unit buffer.
 
                        shmhuge Same as shm, but use huge pages as backing.
 
-                       mmap    Use anonymous memory maps as the buffers.
-                               Allocated through mmap(2).
+                       mmap    Use mmap to allocate buffers. May either be
+                               anonymous memory, or can be file backed if
+                               a filename is given after the option. The
+                               format is mem=mmap:/path/to/file.
+
+                       mmaphuge Use a memory mapped huge file as the buffer
+                               backing. Append filename after mmaphuge, ala
+                               mem=mmaphuge:/hugetlbfs/file
 
                The area allocated is a function of the maximum allowed
-               bs size for the job, multiplied by the io depth given.
+               bs size for the job, multiplied by the io depth given. Note
+               that for shmhuge and mmaphuge to work, the system must have
+               free huge pages allocated. This can normally be checked
+               and set by reading/writing /proc/sys/vm/nr_hugepages on a
+               Linux system. Fio assumes a huge page is 4MiB in size. So
+               to calculate the number of huge pages you need for a given
+               job file, add up the io depth of all jobs (normally one unless
+               iodepth= is used) and multiply by the maximum bs set. Then
+               divide that number by the huge page size. You can see the
+               size of the huge pages in /proc/meminfo. If no huge pages
+               are allocated by having a non-zero number in nr_hugepages,
+               using mmaphuge or shmhuge will fail. Also see hugepage-size.
+
+               mmaphuge also needs to have hugetlbfs mounted and the file
+               location should point there. So if it's mounted in /huge,
+               you would use mem=mmaphuge:/huge/somefile.
+
+hugepage-size=siint
+               Defines the size of a huge page. Must at least be equal
+               to the system setting, see /proc/meminfo. Defaults to 4MiB.
+               Should probably always be a multiple of megabytes, so using
+               hugepage-size=Xm is the preferred way to set this to avoid
+               setting a non-pow-2 bad value.
 
 exitall                When one job finishes, terminate the rest. The default is
                to wait for each job to finish, sometimes that is not the
@@ -380,7 +417,7 @@ create_serialize=bool       If true, serialize the file creating for the jobs.
 create_fsync=bool      fsync the data file after creation. This is the
                        default.
 
-unlink         Unlink the job files when done. fio defaults to doing this,
+unlink=bool    Unlink the job files when done. fio defaults to doing this,
                if it created the file itself.
 
 loops=int      Run the specified number of iterations of this job. Used