From: Stefan Hajnoczi <stefanha@gmail.com>
To: Bug 1321464 <1321464@bugs.launchpad.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [Bug 1321464] Re: qemu/block/qcow2.c:1942: possible performance problem ?
Date: Fri, 23 May 2014 14:27:43 +0200 [thread overview]
Message-ID: <20140523122743.GH1260@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <20140520232105.2195.64239.malone@gac.canonical.com>
On Tue, May 20, 2014 at 11:21:05PM -0000, Max Reitz wrote:
> I can only speak for qcow2 and qcow, but for those places, I don't think
> it is worth fixing. First of all, both are image formats, so the
> bottleneck is generally the disk on which the images are stored and not
> main memory, so an overeager memset should not cause any problems.
>
> For both, the relevant piece of code is in qcow2/qcow_write_compressed()
> which are rarely used anyway (as far as I know) and even if used, they
> have additional overhead due to having to compress data first, so
> “fixing” the memset() won't make them noticibly faster.
I agree. It won't make a noticable difference and the compressed writes
are only done in qemu-img convert, not for running guests.
But patches to change this wouldn't hurt either.
Stefan
next prev parent reply other threads:[~2014-05-23 12:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-20 21:48 [Qemu-devel] [Bug 1321464] [NEW] qemu/block/qcow2.c:1942: possible performance problem ? dcb
2014-05-20 23:21 ` [Qemu-devel] [Bug 1321464] " Max Reitz
2014-05-23 12:27 ` Stefan Hajnoczi [this message]
2017-10-03 9:42 ` Thomas Huth
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=20140523122743.GH1260@stefanha-thinkpad.redhat.com \
--to=stefanha@gmail.com \
--cc=1321464@bugs.launchpad.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).