From: Stefan Hajnoczi <stefanha@gmail.com>
To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
qemu-devel@nongnu.org, Khoa Huynh <khoa@us.ibm.com>,
pbadari@linux.vnet.ibm.com, Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] [PATCH] raw-posix: Linearize direct I/O on Linux NFS
Date: Sat, 16 Apr 2011 09:46:38 +0100 [thread overview]
Message-ID: <BANLkTi=JjDrA6h=M3cu6myy5fa4KNjGS2Q@mail.gmail.com> (raw)
In-Reply-To: <4DA8CE00.3090907@us.ibm.com>
On Sat, Apr 16, 2011 at 12:00 AM, Anthony Liguori <aliguori@us.ibm.com> wrote:
> 3) We have no way to detect when we no longer need a work around which makes
> (2) really unappealing.
I agree.
> 4) That leaves us with:
> a) waiting for NFS to get fixed properly and just living with worse
> performance on older kernels
>
> b) having a user-tunable switch to enable bouncing
>
> I really dislike the idea of (b) because we're stuck with it forever and
> it's yet another switch for people to mistakenly depend on.
The user-tunable switch is potentially interesting for performance
troubleshooting. We have seen another file system which has issues
with vectored direct I/O. It would have been much easier to identify
the problem by telling the user "Try running it with linearize=on and
see if it makes a difference".
But let's try harder on linux-nfs.
Stefan
next prev parent reply other threads:[~2011-04-16 8:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-15 13:40 [Qemu-devel] [PATCH] raw-posix: Linearize direct I/O on Linux NFS Stefan Hajnoczi
2011-04-15 15:05 ` Christoph Hellwig
2011-04-15 15:26 ` Stefan Hajnoczi
2011-04-15 15:34 ` Christoph Hellwig
2011-04-15 16:10 ` Anthony Liguori
2011-04-15 16:17 ` Stefan Hajnoczi
2011-04-15 17:27 ` Christoph Hellwig
2011-04-15 16:23 ` Badari Pulavarty
2011-04-15 17:29 ` Christoph Hellwig
2011-04-15 22:21 ` Badari Pulavarty
2011-04-15 23:00 ` Anthony Liguori
2011-04-15 23:33 ` Badari Pulavarty
2011-04-16 2:05 ` Christoph Hellwig
2011-04-16 8:46 ` Stefan Hajnoczi [this message]
2011-04-16 2:03 ` Christoph Hellwig
2011-04-15 18:09 ` Anthony Liguori
2011-04-15 18:25 ` Badari Pulavarty
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