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Date: Mon, 21 Jan 2013 17:29:35 +0000
From: Alex Bligh <alex@alex.org.uk>
Reply-To: Alex Bligh <alex@alex.org.uk>
To: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
cc: linux-nfs@vger.kernel.org, ian.campbell@citrix.com,
        Alex Bligh <alex@alex.org.uk>
Subject: Re: Fatal crash with NFS, AIO & tcp retransmit
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Trond,

--On 21 January 2013 17:20:36 +0000 "Myklebust, Trond" 
<Trond.Myklebust@netapp.com> wrote:

> That is correct. If you want zero-copy, then O_DIRECT is your thing
> (with or without aio). Otherwise, the kernel will always write to disk
> by copying through the page cache.

Thanks. From the crash dump it appeared to be accessing mapped memory
somehow, so I'll see whether QEMU is in fact using O_DIRECT contrary
to documentation.

-- 
Alex Bligh