[PATCH] Add thinktime_blocks

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index a5caea3db7a6201d74311b50a5d5d56bbbb77311..c9d29f299bd4109fcbcf3c504925986d28979c18 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -319,7 +319,13 @@ 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
 
 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.
 
 
 rate=int       Cap the bandwidth used by this job to this number of KiB/sec.
 


@@ -357,11 +363,41 @@ mem=str           Fio can use various types of memory as the io unit buffer.
                        shm     Use shared memory as the buffers. Allocated
                                through shmget(2).
 
                        shm     Use shared memory as the buffers. Allocated
                                through shmget(2).
 

-                       mmap    Use anonymous memory maps as the buffers.
-                               Allocated through mmap(2).
+                       shmhuge Same as shm, but use huge pages as backing.
+
+                       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
 
                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
 
 exitall                When one job finishes, terminate the rest. The default is
                to wait for each job to finish, sometimes that is not the