From: Jamie Lokier <jamie@shareable.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Avi Kivity <avi@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] barriers: block layer preparations
Date: Tue, 5 May 2009 23:49:04 +0100 [thread overview]
Message-ID: <20090505224904.GI7574@shareable.org> (raw)
In-Reply-To: <20090505205716.GA24320@lst.de>
Christoph Hellwig wrote:
> > A barrier for read can be meaningful if the guest wishes to read a
> > known-to-be-stable write. I don't think any guest can make use of this
> > though.
>
> I don't know of any storage standard having anything like this or any
> OS taking advantage of it. I'd be happy to review anything like that,
> though.
Several OSes have O_RSYNC, meaning reads hit the storage instead of
the OS cache. I don't know if they bypass storage caches, but the
purpose seems to be to verify writes, and they will certainly bypass
storage caches if the OS or user turns off the storage caches.
-- Jamie
next prev parent reply other threads:[~2009-05-05 22:49 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-05 12:08 [Qemu-devel] [PATCH 0/3] write barrier support Christoph Hellwig
2009-05-05 12:08 ` [Qemu-devel] barriers: block layer preparations Christoph Hellwig
2009-05-05 13:51 ` Avi Kivity
2009-05-05 15:38 ` Jamie Lokier
2009-05-05 15:49 ` Avi Kivity
2009-05-05 16:00 ` Jamie Lokier
2009-05-05 20:57 ` Christoph Hellwig
2009-05-05 22:49 ` Jamie Lokier [this message]
2009-05-05 12:08 ` [Qemu-devel] [PATCH 2/3] barriers: block-raw-posix barrier support Christoph Hellwig
2009-05-05 12:33 ` Jamie Lokier
2009-05-05 13:29 ` Christoph Hellwig
2009-05-05 16:00 ` Jamie Lokier
2009-05-05 12:09 ` [Qemu-devel] [PATCH 3/3] barriers: virtio Christoph Hellwig
2009-05-05 13:53 ` [Qemu-devel] [PATCH 0/3] write barrier support Avi Kivity
2009-05-05 21:00 ` Christoph Hellwig
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