Messages in this thread | | | Date | Tue, 17 Jul 2012 12:11:15 +0100 | Subject | Re: [PATCH 0/5] Add vhost-blk support | From | Stefan Hajnoczi <> |
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On Tue, Jul 17, 2012 at 10:21 AM, Asias He <asias@redhat.com> wrote: > On 07/17/2012 04:52 PM, Paolo Bonzini wrote: >> >> Il 17/07/2012 10:29, Asias He ha scritto: >>> >>> So, vhost-blk at least saves ~6 syscalls for us in each request. >> >> >> Are they really 6? If I/O is coalesced by a factor of 3, for example >> (i.e. each exit processes 3 requests), it's really 2 syscalls per request. > > > Well. I am counting the number of syscalls in one notify and response > process. Sure the IO can be coalesced.
Linux AIO also supports batching in io_submit() and io_getevents(). Depending on the request pattern in the vring when you process it, you should be able to do better than 1 set of syscalls per host I/O request.
Are you taking advantage of that at the moment in your userspace benchmark?
Stefan
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