Re: [PATCH 0/5] Add vhost-blk support

From: Stefan Hajnoczi
Date: Tue Jul 17 2012 - 07:11:14 EST

On Tue, Jul 17, 2012 at 10:21 AM, Asias He <asias@xxxxxxxxxx> 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

Are you taking advantage of that at the moment in your userspace benchmark?

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