On 11/15/2016 04:32 AM, Stefan Hajnoczi wrote:
> 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.
>
I removed all the pinning and restored the guest to a "normal"
configuration.
QEMU_AIO_POLL_MAX_NS IOPs
unset 25,553
1 28,684
2 38,213
4 29,413
8 38,612
16 30,578
32 30,145
64 41,637
128 28,554
256 29,661
512 39,178
1,024 29,644
2,048 37,190
4,096 29,838
8,192 38,581
16,384 37,793
32,768 20,332
65,536 35,755
--
Karl Rister <[email protected]>
