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Date: Fri, 12 Dec 2008 01:27:21 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool
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To: Christoph Hellwig <hch@lst.de>
Cc: qemu-devel@nongnu.org, kvm-devel <kvm@vger.kernel.org>, Gerd Hoffmann <kraxel@redhat.com>

On Thu, Dec 11, 2008 at 10:32:13PM +0100, Christoph Hellwig wrote:
> Mainline kernel aio only implements O_DIRECT.  Some RHEL version had
> support for buffered kernel AIO.

Not just RHEL, I'm sure SLES supported this too and it was quite
cleanly implemented, not sure why this wasn't picked up by mainline.

At the light of this preadv/pwritev or having the file opened by each
thread (if proven safe with nfs) remains the only option. Zerocopy dma
must be supported without O_DIRECT too even if it's probably more
important when O_DIRECT is on.