Messages in this thread | | | Date | Wed, 17 Mar 2010 11:10:53 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter |
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On 03/17/2010 10:49 AM, Christoph Hellwig wrote: > On Tue, Mar 16, 2010 at 01:08:28PM +0200, Avi Kivity wrote: > >> If the batch size is larger than the virtio queue size, or if there are >> no flushes at all, then yes the huge write cache gives more opportunity >> for reordering. But we're already talking hundreds of requests here. >> > Yes. And rememember those don't have to come from the same host. Also > remember that we rather limit execssive reodering of O_DIRECT requests > in the I/O scheduler because they are "synchronous" type I/O while > we don't do that for pagecache writeback. >
Maybe we should relax that for kvm. Perhaps some of the problem comes from the fact that we call io_submit() once per request.
> And we don't have unlimited virtio queue size, in fact it's quite > limited. >
That can be extended easily if it fixes the problem.
-- error compiling committee.c: too many arguments to function
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