Add vsync io engine

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index d5fb52cfb0f9f931db588c78d92e81a95480f2ca..3d6b354b87b7df40f723c497ab82b1424cd287f6 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -262,6 +262,10 @@ filesize=siint     Individual file sizes. May be a range, in which case fio
                and limited to 'size' in total (if that is given). If not
                given, each created file is the same size.
 
+fill_device=bool Sets size to something really large and waits for ENOSPC (no
+               space left on device) as the terminating condition. Only makes
+                sense with sequential write.
+
 blocksize=siint
 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
@@ -281,6 +285,30 @@ bsrange=irange     Instead of giving a single block size, specify a range
                writes, however a second range can be given after a comma.
                See bs=.
 
+bssplit=str    Sometimes you want even finer grained control of the
+               block sizes issued, not just an even split between them.
+               This option allows you to weight various block sizes,
+               so that you are able to define a specific amount of
+               block sizes issued. The format for this option is:
+
+                       bssplit=blocksize/percentage:blocksize/percentage
+
+               for as many block sizes as needed. So if you want to define
+               a workload that has 50% 64k blocks, 10% 4k blocks, and
+               40% 32k blocks, you would write:
+
+                       bssplit=4k/10:64k/50:32k/40
+
+               Ordering does not matter. If the percentage is left blank,
+               fio will fill in the remaining values evenly. So a bssplit
+               option like this one:
+
+                       bssplit=4k/50:1k/:32k/
+
+               would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
+               always add up to 100, if bssplit is given a range that adds
+               up to more, it will error out.
+
 blocksize_unaligned
 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
@@ -316,6 +344,8 @@ ioengine=str        Defines how the job issues io to the file. The following
 
                        psync   Basic pread(2) or pwrite(2) io.
 
+                       vsync   Basic readv(2) or writev(3) IO.
+
                        libaio  Linux native asynchronous io.
 
                        posixaio glibc posix asynchronous io.
@@ -374,8 +404,9 @@ iodepth=int This defines how many io units to keep in flight against
                concurrency.
 
 iodepth_batch=int This defines how many pieces of IO to submit at once.
-               It defaults to the same as iodepth, but can be set lower
-               if one so desires.
+               It defaults to 1 which means that we submit each IO
+               as soon as it is available, but can be raised to submit
+               bigger batches of IO at the time.
 
 iodepth_low=int        The low water mark indicating when to start filling
                the queue again. Defaults to the same as iodepth, meaning
@@ -601,15 +632,6 @@ verify=str If writing to a file, fio can verify the file contents
                                (timestamp, block number etc.). The block
                                number is verified.
 
-                       pattern Fill the IO buffers with a specific pattern,
-                               that we can use to verify. Depending on the
-                               width of the pattern, fio will fill 1/2/3/4
-                               bytes of the buffer at the time. The pattern
-                               cannot be larger than a 32-bit quantity. The
-                               given pattern is given as a postfix to this
-                               option, ala: verify=pattern:0x5a. It accepts
-                               both hex and dec values.
-
                        null    Only pretend to verify. Useful for testing
                                internals with ioengine=null, not for much
                                else.
@@ -635,6 +657,14 @@ verify_interval=siint      Write the verification header at a finer granularity
                        size of header_interval. blocksize should divide this
                        evenly.
 
+verify_pattern=int     If set, fio will fill the io buffers with this
+               pattern. Fio defaults to filling with totally random
+               bytes, but sometimes it's interesting to fill with a known
+               pattern for io verification purposes. Depending on the
+               width of the pattern, fio will fill 1/2/3/4 bytes of the
+               buffer at the time. The verify_pattern cannot be larger than
+               a 32-bit quantity.
+
 verify_fatal=bool      Normally fio will keep checking the entire contents
                before quitting on a block verification failure. If this
                option is set, fio will exit the job on the first observed