From: Christoph Hellwig <hch@lst.de>
To: Jamie Lokier <jamie@shareable.org>
Cc: Christoph Hellwig <hch@lst.de>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 2/3] barriers: block-raw-posix barrier support
Date: Tue, 5 May 2009 15:29:44 +0200 [thread overview]
Message-ID: <20090505132944.GA3416@lst.de> (raw)
In-Reply-To: <20090505123311.GD25328@shareable.org>
On Tue, May 05, 2009 at 01:33:11PM +0100, Jamie Lokier wrote:
> You don't need two fdatasyncs if the barrier request is just a
> barrier, no data write, used only to flush previously written data by
> a guest's fsync/fdatasync implementation.
Yeah. I'll put that optimization in after some testing.
> This is the best argument yet for having distinct "barrier" and "sync"
> operations. "Barrier" is for ordering I/O, such as journalling
> filesystems.
Doesn't really help as long as we're using the normal Posix filesystem
APIs on the host. The only way to guarantee ordering of multiple
*write* systen calls is to call f(data)sync between them.
next prev parent reply other threads:[~2009-05-05 13:29 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
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 [this message]
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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