On Mon, Nov 14, 2016 at 09:52:00PM +0100, Paolo Bonzini wrote: > On 14/11/2016 21:12, Karl Rister wrote: > > 256 46,929 > > 512 35,627 > > 1,024 46,477 > > 2,000 35,247 > > 2,048 46,322 > > 4,000 46,540 > > 4,096 46,368 > > 8,000 47,054 > > 8,192 46,671 > > 16,000 46,466 > > 16,384 32,504 > > 32,000 20,620 > > 32,768 20,807 > > Huh, it breaks down exactly when it should start going faster > (10^9/46000 = ~21000).
Could it be because we're not breaking the polling loop for BHs, new timers, or aio_notify()? Once that is fixed polling should achieve maximum performance when QEMU_AIO_MAX_POLL_NS is at least as long as the duration of a request. This is logical if there are enough pinned CPUs so the polling thread can run flat out. Stefan
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