All of lore.kernel.org
 help / color / mirror / Atom feed
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

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4861156B.30707@suse.de \
    --to=kwolf@suse.de \
    --cc=Laurent.Vivier@bull.net \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.