From: Kevin Wolf <kwolf@suse.de>
To: Laurent Vivier <Laurent.Vivier@bull.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] qcow2: improve I/O performance with cache=off
Date: Tue, 24 Jun 2008 17:40:27 +0200 [thread overview]
Message-ID: <4861156B.30707@suse.de> (raw)
In-Reply-To: <1213972680.3859.34.camel@frecb07144>
Hi Laurent,
Laurent Vivier schrieb:
> this patch improves qcow2 I/O performance when used with cache=off.
Why do you think this patch helps only for cache=off? I have applied
your patch to Xen ioemu (which has no cache=off / O_DIRECT yet) and
I certainly do see a performance gain for large block sizes (using dd).
With small block sizes like 512 bytes or 1k I lose a bit of perfomance,
though.
bonnie++ shows slightly better numbers with this patch, too. In the
case of block reads the improvement is huge and I even got double
throughput.
I also had a look at your code and it seems fine to me. (Except that
the aio callback handlers become even longer, but that is a different
problem...)
Kevin
next prev parent reply other threads:[~2008-06-24 15:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-20 14:38 [Qemu-devel] [PATCH] qcow2: improve I/O performance with cache=off Laurent Vivier
2008-06-23 2:50 ` Avi Kivity
2008-06-24 15:40 ` Kevin Wolf [this message]
2008-06-24 16:40 ` Laurent Vivier
2008-06-25 8:43 ` Kevin Wolf
2008-06-25 8:59 ` Laurent Vivier
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