From: Kevin Wolf <kwolf@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, mst@redhat.com,
anthony@codemonkey.ws, rusty@rustcorp.com.au
Subject: Re: [PATCH 2/2] virtio-blk: disable write cache if not negotiated
Date: Tue, 03 Jul 2012 15:49:48 +0200 [thread overview]
Message-ID: <4FF2F87C.6010600@redhat.com> (raw)
In-Reply-To: <1341321642-24598-3-git-send-email-pbonzini@redhat.com>
Am 03.07.2012 15:20, schrieb Paolo Bonzini:
> If the guest does not support flushes, we should run in writethrough mode.
> The setting is temporary until the next reset, so that for example the
> BIOS will run in writethrough mode while Linux will run with a writeback
> cache.
>
> VIRTIO_BLK_F_FLUSH has been introduced in Linux 2.6.32 (in 2009) and
> was backported to RHEL/CentOS 5.6 (in 2010). The Windows drivers have
> two bugs, which I reported on the Red Hat Bugzilla as bugs 837321 and
> 837324. With these patches they will suffer a performance hit but
> gain correctness.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
I generally like the idea for a default, but doesn't this override even
an explicit cache=writeback? Are we sure that we want this?
Kevin
WARNING: multiple messages have this Message-ID (diff)
From: Kevin Wolf <kwolf@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: anthony@codemonkey.ws, rusty@rustcorp.com.au,
qemu-devel@nongnu.org, kvm@vger.kernel.org, mst@redhat.com
Subject: Re: [Qemu-devel] [PATCH 2/2] virtio-blk: disable write cache if not negotiated
Date: Tue, 03 Jul 2012 15:49:48 +0200 [thread overview]
Message-ID: <4FF2F87C.6010600@redhat.com> (raw)
In-Reply-To: <1341321642-24598-3-git-send-email-pbonzini@redhat.com>
Am 03.07.2012 15:20, schrieb Paolo Bonzini:
> If the guest does not support flushes, we should run in writethrough mode.
> The setting is temporary until the next reset, so that for example the
> BIOS will run in writethrough mode while Linux will run with a writeback
> cache.
>
> VIRTIO_BLK_F_FLUSH has been introduced in Linux 2.6.32 (in 2009) and
> was backported to RHEL/CentOS 5.6 (in 2010). The Windows drivers have
> two bugs, which I reported on the Red Hat Bugzilla as bugs 837321 and
> 837324. With these patches they will suffer a performance hit but
> gain correctness.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
I generally like the idea for a default, but doesn't this override even
an explicit cache=writeback? Are we sure that we want this?
Kevin
next prev parent reply other threads:[~2012-07-03 13:49 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-03 13:20 [QEMU PATCH 0/2] virtio-blk: writeback cache enable improvements Paolo Bonzini
2012-07-03 13:20 ` [Qemu-devel] " Paolo Bonzini
2012-07-03 13:20 ` [PATCH 1/2] virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE Paolo Bonzini
2012-07-03 13:20 ` [Qemu-devel] " Paolo Bonzini
2012-07-03 13:46 ` Kevin Wolf
2012-07-03 13:46 ` [Qemu-devel] " Kevin Wolf
2012-07-03 13:54 ` Paolo Bonzini
2012-07-03 13:54 ` [Qemu-devel] " Paolo Bonzini
2012-07-03 13:20 ` [PATCH 2/2] virtio-blk: disable write cache if not negotiated Paolo Bonzini
2012-07-03 13:20 ` [Qemu-devel] " Paolo Bonzini
2012-07-03 13:49 ` Kevin Wolf [this message]
2012-07-03 13:49 ` Kevin Wolf
2012-07-03 13:51 ` Paolo Bonzini
2012-07-03 13:51 ` [Qemu-devel] " Paolo Bonzini
2012-07-04 10:16 ` Kevin Wolf
2012-07-04 10:16 ` Kevin Wolf
2012-07-04 12:21 ` Paolo Bonzini
2012-07-04 12:21 ` Paolo Bonzini
2012-07-04 12:50 ` Kevin Wolf
2012-07-04 12:50 ` [Qemu-devel] " Kevin Wolf
2012-07-04 13:20 ` Paolo Bonzini
2012-07-04 13:20 ` Paolo Bonzini
2012-07-23 16:32 ` [QEMU PATCH 0/2] virtio-blk: writeback cache enable improvements Paolo Bonzini
2012-07-23 16:32 ` [Qemu-devel] " Paolo Bonzini
2012-08-01 15:52 ` Paolo Bonzini
2012-08-01 15:52 ` [Qemu-devel] " Paolo Bonzini
2012-08-01 16:25 ` Kevin Wolf
2012-08-01 16:25 ` [Qemu-devel] " Kevin Wolf
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