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From: Badari Pulavarty <pbadari@us.ibm.com>
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Date: Fri, 15 Apr 2011 09:23:54 -0700
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Subject: Re: [Qemu-devel] [PATCH] raw-posix: Linearize direct I/O
	on	Linux	NFS
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To: Christoph Hellwig <hch@lst.de>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Khoa Huynh <khoa@us.ibm.com>

On Fri, 2011-04-15 at 17:34 +0200, Christoph Hellwig wrote:
> On Fri, Apr 15, 2011 at 04:26:41PM +0100, Stefan Hajnoczi wrote:
> > On Fri, Apr 15, 2011 at 4:05 PM, Christoph Hellwig <hch@lst.de> wrote:
> > > NAK. ?Just wait for the bloody NFS client fix to get in instead of
> > > adding crap like that.
> > 
> > That's totally fine if NFS client will be fixed in the near future but
> > this doesn't seem likely:
> > 
> > http://www.spinics.net/lists/linux-nfs/msg20462.html
> 
> The code to use preadv/pwritev has been in qemu for over 2 years,
> and it took people to notice the NFS slowdown until now, so don't
> expect it to be fixed three days layer.

True. That brings up a different question - whether we are doing
enough testing on mainline QEMU :(

> I can't event see you in the relevent threads arguing for getting it
> fixed, so don't complain. 

I asked Stefan to work on a QEMU patch - since my QEMU skills are
limited and Stefan is more appropriate person to deal with QEMU :)

As mentioned earlier, we don't see performance with any temporary
solutions suggested so far (RPC table slot + ASYNC) comes anywhere
close to readv/writev support patch or linearized QEMU.

Thanks,
Badari