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 request. Are you taking advantage of that at the moment in your userspace benchmark? Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
