qemu-img bench: Sequential writes

This extends qemu-img bench with an option that makes it use sequential
writes instead of reads for the test run.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/qemu-img.texi b/qemu-img.texi
index b6b28e3542..c477fbf1c3 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -131,16 +131,21 @@ Skip the creation of the target volume
 Command description:
 
 @table @option
-@item bench [-c @var{count}] [-d @var{depth}] [-f @var{fmt}] [-n] [-q] [-s @var{buffer_size}] [-t @var{cache}] @var{filename}
+@item bench [-c @var{count}] [-d @var{depth}] [-f @var{fmt}] [-n] [--pattern=@var{pattern}] [-q] [-s @var{buffer_size}] [-t @var{cache}] [-w] @var{filename}
 
-Run a simple sequential read benchmark on the specified image. A total number
-of @var{count} I/O requests is performed, each @var{buffer_size} bytes in size,
-and with @var{depth} requests in parallel.
+Run a simple sequential I/O benchmark on the specified image. If @code{-w} is
+specified, a write test is performed, otherwise a read test is performed.
+
+A total number of @var{count} I/O requests is performed, each @var{buffer_size}
+bytes in size, and with @var{depth} requests in parallel.
 
 If @code{-n} is specified, the native AIO backend is used if possible. On
 Linux, this option only works if @code{-t none} or @code{-t directsync} is
 specified as well.
 
+For write tests, by default a buffer filled with zeros is written. This can be
+overridden with a pattern byte specified by @var{pattern}.
+
 @item check [-f @var{fmt}] [--output=@var{ofmt}] [-r [leaks | all]] [-T @var{src_cache}] @var{filename}
 
 Perform a consistency check on the disk image @var{filename}. The command can