Add support for 'bssplit' option, fine grained block size contrl

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index d5fb52cfb0f9f931db588c78d92e81a95480f2ca..569b998f215b78d41a36ac71d78f1506a013af4e 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -281,6 +281,30 @@ 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