Re: [PATCH] vhost: Add polling mode

Michael S. Tsirkin
2014-08-20T11:05:15Z

On Tue, Aug 19, 2014 at 11:36:31AM +0300, Razya Ladelsky wrote:
> > That was just one example. There many other possibilities. Either
> > actually make the systems load all host CPUs equally, or divide
> > throughput by host CPU.
> >
>
> The polling patch adds this capability to vhost, reducing costly exit
> overhead when the vm is loaded.
>
> In order to load the vm I ran netperf with msg size of 256:
>
> Without polling: 2480 Mbits/sec, utilization: vm - 100% vhost - 64%
> With Polling: 4160 Mbits/sec, utilization: vm - 100% vhost - 100%
>
> Therefore, throughput/cpu without polling is 15.1, and 20.8 with polling.
>

Can you please present results in a form that makes
it possible to see the effect on various configurations
and workloads?

Here's one example where this was done:
https://lkml.org/lkml/2014/8/14/495

You really should also provide data about your host
configuration (missing in the above link).

> My intention was to load vhost as close as possible to 100% utilization
> without polling, in order to compare it to the polling utilization case
> (where vhost is always 100%).
> The best use case, of course, would be when the shared vhost thread work
> (TBD) is integrated and then vhost will actually be using its polling
> cycles to handle requests of multiple devices (even from multiple vms).
>
> Thanks,
> Razya

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MST