From: Stefan Hajnoczi <stefanha@gmail.com>
To: Alexander Graf <agraf@suse.de>
Cc: Kevin Wolf <kwolf@redhat.com>,
Qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] Default cache mode
Date: Wed, 29 Jun 2011 14:57:17 +0100 [thread overview]
Message-ID: <BANLkTikNkeWECz-cEMS9qcNKk-hv95PSYg@mail.gmail.com> (raw)
In-Reply-To: <513A5DA9-54CC-4D7C-9715-2F131087F3EF@suse.de>
On Wed, Jun 29, 2011 at 1:21 PM, Alexander Graf <agraf@suse.de> wrote:
> On 29.06.2011, at 13:59, Kevin Wolf wrote:
>> I'm not entirely sure if I should suggest writeback or none as the new
>> default, but I think it could make sense to change it.
>
> None as default would be a bad choice, as not all underlying file systems support it. Try cache=none on tmpfs or nfs. It will just fail on you.
> What I'd personally like to see is some sort of detection that can determine which caching mode would perform best. So it would do cache=none when it makes sense (raw block device), otherwise cache=writeback.
O_DIRECT works on the Linux NFS client. The performance currently
isn't great with vectored I/O (which QEMU does) but there is work
ongoing to improve it.
Your point makes sense though. The default (no explicit cache=)
should mean "the most appropriate caching mode".
Stefan
next prev parent reply other threads:[~2011-06-29 13:57 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-29 11:59 [Qemu-devel] Default cache mode Kevin Wolf
2011-06-29 12:06 ` Anthony Liguori
2011-06-29 12:16 ` Kevin Wolf
2011-06-29 12:23 ` Anthony Liguori
2011-06-29 12:32 ` Kevin Wolf
2011-06-29 13:51 ` Christoph Hellwig
2011-06-29 14:17 ` Michael Tokarev
2011-06-29 14:50 ` Christoph Hellwig
2011-06-29 15:07 ` Michael Tokarev
2011-06-29 13:50 ` Christoph Hellwig
2011-06-29 14:13 ` Anthony Liguori
2011-06-29 14:47 ` Christoph Hellwig
2011-06-29 16:03 ` Stefan Hajnoczi
2011-06-29 13:53 ` Frediano Ziglio
2011-06-29 14:11 ` Kevin Wolf
2011-06-29 14:12 ` Christoph Hellwig
2011-06-29 14:21 ` Kevin Wolf
2011-06-29 13:49 ` Christoph Hellwig
2011-06-29 12:08 ` Anthony Liguori
2011-06-29 13:55 ` Christoph Hellwig
2011-06-29 14:20 ` Anthony Liguori
2011-06-29 14:52 ` Christoph Hellwig
2011-06-29 15:26 ` Anthony Liguori
2011-06-29 12:21 ` Alexander Graf
2011-06-29 13:57 ` Stefan Hajnoczi [this message]
2011-06-29 14:05 ` Alexander Graf
2011-06-29 12:52 ` Stefan Hajnoczi
2011-06-29 13:56 ` Christoph Hellwig
2011-06-29 13:00 ` Avi Kivity
2011-06-29 13:05 ` Anthony Liguori
2011-06-29 13:30 ` Avi Kivity
2011-06-29 13:11 ` Kevin Wolf
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=BANLkTikNkeWECz-cEMS9qcNKk-hv95PSYg@mail.gmail.com \
--to=stefanha@gmail.com \
--cc=Qemu-devel@nongnu.org \
--cc=agraf@suse.de \
--cc=avi@redhat.com \
--cc=hch@lst.de \
--cc=kwolf@redhat.com \
--cc=stefanha@linux.vnet.ibm.com \
/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).