Add possibility to make sequential IO "holed"
For sequential IO, it is now possible to add a number of bytes to
be skipped for every block read or written. Using:
bs=8k
rw=read:8k
will first read 0k->8k, then 16k->24k, and so on. This skips 8k
for every 'bs' sized block read. Similar for writes, doing
bs=4k
rw=write:4k
will write 0k->4k, then 8k->12k, etc. End result being that every
other block is written, in a sequential fashion.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/HOWTO b/HOWTO
index 72a29a9..a1b2e8c 100644
--- a/HOWTO
+++ b/HOWTO
@@ -319,8 +319,12 @@
a number of IO's to do before getting a new offset, this is
one by appending a ':<nr>' to the end of the string given.
For a random read, it would look like 'rw=randread:8' for
- passing in an offset modifier with a value of 8. See the
- 'rw_sequencer' option.
+ passing in an offset modifier with a value of 8. If the
+ postfix is used with a sequential IO pattern, then the value
+ specified will be added to the generated offset for each IO.
+ For instance, using rw=write:4k will skip 4k for every
+ write. It turns sequential IO into sequential IO with holes.
+ See the 'rw_sequencer' option.
rw_sequencer=str If an offset modifier is given by appending a number to
the rw=<str> line, then this option controls how that