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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