From: Paolo Bonzini <pbonzini@redhat.com>
To: Liu Yuan <namei.unix@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
qemu-devel@nongnu.org,
MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Subject: Re: [Qemu-devel] [PATCH] sheepdog: implement direct write semantics
Date: Fri, 11 Jan 2013 04:34:13 -0500 (EST) [thread overview]
Message-ID: <1738190588.4885859.1357896853370.JavaMail.root@redhat.com> (raw)
In-Reply-To: <50EFD597.90106@gmail.com>
----- Messaggio originale -----
> Da: "Liu Yuan" <namei.unix@gmail.com>
> A: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: "Kevin Wolf" <kwolf@redhat.com>, "Stefan Hajnoczi" <stefanha@gmail.com>, qemu-devel@nongnu.org, "MORITA Kazutaka"
> <morita.kazutaka@lab.ntt.co.jp>
> Inviato: Venerdì, 11 gennaio 2013 10:04:23
> Oggetto: Re: [Qemu-devel] [PATCH] sheepdog: implement direct write semantics
>
> On 01/11/2013 05:00 PM, Paolo Bonzini wrote:
> > That's not correct. Try hdparm with an IDE disk, or sysfs with a
> > SCSI disk (recent kernels will also support sysfs with an IDE or
> > virtio-blk disk) and you'll see that it changes.
>
> Okay, at least at startup, even with cache=writehtough set, I saw
> bdrv_enable_write_cache() returns true from sd_open(). So you mean
> this will be reset later (after sd_open())?
It is always true for the protocol. It is not always true for the format.
This is correct. qcow2 can do some writes in writeback mode, but they
will always be followed by a flush before the write is reported to the
guest. It is a bit faster, and does not lose any correctness.
Paolo
next prev parent reply other threads:[~2013-01-11 9:34 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-19 18:29 [Qemu-devel] [PATCH] sheepdog: implement direct write semantics Liu Yuan
2012-12-25 7:47 ` MORITA Kazutaka
2012-12-25 8:26 ` Liu Yuan
2012-12-25 8:45 ` Liu Yuan
2013-01-03 13:43 ` Liu Yuan
2013-01-04 16:38 ` Stefan Hajnoczi
2013-01-05 4:40 ` Liu Yuan
2013-01-05 5:29 ` Liu Yuan
2013-01-05 7:56 ` Liu Yuan
2013-01-07 12:31 ` Stefan Hajnoczi
2013-01-08 5:28 ` Liu Yuan
2013-01-07 13:23 ` Kevin Wolf
2013-01-08 5:42 ` Liu Yuan
2013-01-08 9:40 ` Stefan Hajnoczi
2013-01-08 9:45 ` Liu Yuan
2013-01-08 10:00 ` Kevin Wolf
2013-01-08 10:39 ` Liu Yuan
2013-01-08 10:51 ` Kevin Wolf
2013-01-08 11:08 ` Liu Yuan
2013-01-08 11:19 ` Kevin Wolf
2013-01-08 11:35 ` Liu Yuan
2013-01-08 12:12 ` Kevin Wolf
2013-01-08 13:18 ` Liu Yuan
2013-01-08 13:23 ` Liu Yuan
2013-01-09 10:25 ` Paolo Bonzini
2013-01-09 10:36 ` Liu Yuan
2013-01-09 10:40 ` Paolo Bonzini
2013-01-09 10:46 ` Liu Yuan
2013-01-09 10:58 ` Liu Yuan
2013-01-09 11:10 ` Paolo Bonzini
2013-01-09 12:07 ` Liu Yuan
2013-01-09 12:10 ` Liu Yuan
2013-01-09 12:16 ` Liu Yuan
2013-01-09 12:42 ` Kevin Wolf
2013-01-09 13:04 ` Liu Yuan
2013-01-09 15:10 ` Paolo Bonzini
2013-01-10 5:38 ` Liu Yuan
2013-01-11 7:52 ` MORITA Kazutaka
2013-01-11 8:07 ` Liu Yuan
2013-01-11 9:00 ` Paolo Bonzini
2013-01-11 9:04 ` Liu Yuan
2013-01-11 9:34 ` Paolo Bonzini [this message]
2013-01-11 9:38 ` Liu Yuan
2013-01-11 9:40 ` Paolo Bonzini
2013-01-11 9:32 ` Kevin Wolf
2013-01-10 15:25 ` Jamie Lokier
2013-01-10 15:31 ` Paolo Bonzini
2013-01-10 17:22 ` Jamie Lokier
2013-01-09 11:10 ` Kevin Wolf
2013-01-09 10:23 ` Paolo Bonzini
2013-01-10 15:12 ` Jamie Lokier
2013-01-10 15:21 ` Kevin Wolf
2013-01-10 8:03 ` [Qemu-devel] [PATCH v2] " Liu Yuan
2013-01-10 9:04 ` Stefan Hajnoczi
2013-01-11 7:35 ` MORITA Kazutaka
2013-01-11 9:23 ` 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=1738190588.4885859.1357896853370.JavaMail.root@redhat.com \
--to=pbonzini@redhat.com \
--cc=kwolf@redhat.com \
--cc=morita.kazutaka@lab.ntt.co.jp \
--cc=namei.unix@gmail.com \
--cc=qemu-devel@nongnu.org \
--cc=stefanha@gmail.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).