[PATCH] Unlink and directory fix

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 2616156d1234017a1d08da368c3bb461c29fcf0a..1b34c283af0f385e00407a9167c6ec02820ad4a1 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -218,22 +218,22 @@ size=siint        The total size of file io for this job. This may describe
                size if larger than the current file size. If this parameter
                is not given and the file exists, the file size will be used.
 
                size if larger than the current file size. If this parameter
                is not given and the file exists, the file size will be used.
 

-bs=siint       The block size used for the io units. Defaults to 4k.
-
-read_bs=siint
-write_bs=siint If the workload is a mixed read-write workload, you can use
-               these options to set separate block sizes.
+bs=siint       The block size used for the io units. Defaults to 4k. Values
+               can be given for both read and writes. If a single siint is
+               given, it will apply to both. If a second siint is specified
+               after a comma, it will apply to writes only. In other words,
+               the format is either bs=read_and_write or bs=read,write.
+               bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
+               for writes. If you only wish to set the write size, you
+               can do so by passing an empty read size - bs=,8k will set
+               8k for writes and leave the read default value.

 
 bsrange=irange Instead of giving a single block size, specify a range
                and fio will mix the issued io block sizes. The issued
                io unit will always be a multiple of the minimum value
 
 bsrange=irange Instead of giving a single block size, specify a range
                and fio will mix the issued io block sizes. The issued
                io unit will always be a multiple of the minimum value

-               given (also see bs_unaligned).
-
-read_bsrange=irange
-write_bsrange=irange
-               If the workload is a mixed read-write workload, you can use
-               one of these options to set separate block size ranges for
-               reads and writes.
+               given (also see bs_unaligned). Applies to both reads and
+               writes, however a second range can be given after a comma.
+               See bs=.

 
 bs_unaligned   If this option is given, any byte size value within bsrange
                may be used as a block range. This typically wont work with
 
 bs_unaligned   If this option is given, any byte size value within bsrange
                may be used as a block range. This typically wont work with


@@ -264,6 +264,10 @@ ioengine=str       Defines how the job issues io to the file. The following
                                we use read(2) and write(2) for asynchronous
                                io.
 
                                we use read(2) and write(2) for asynchronous
                                io.
 

+                       null    Doesn't transfer any data, just pretends
+                               to. This is mainly used to exercise fio
+                               itself and for debugging/testing purposes.
+

 iodepth=int    This defines how many io units to keep in flight against
                the file. The default is 1 for each file defined in this
                job, can be overridden with a larger value for higher
 iodepth=int    This defines how many io units to keep in flight against
                the file. The default is 1 for each file defined in this
                job, can be overridden with a larger value for higher


@@ -315,7 +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.
 


@@ -353,11 +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


@@ -374,7 +414,7 @@ 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.
 
 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
                if it created the file itself.
 
 loops=int      Run the specified number of iterations of this job. Used