Re: [PATCH] vhost: Add polling mode

Michael S. Tsirkin
2014-08-17T12:58:09Z

On Sun, Aug 17, 2014 at 03:35:39PM +0300, Razya Ladelsky wrote:
> > >
> > > Hi Michael,
> > >
> > > Sorry for the delay, had some problems with my mailbox, and I realized
>
> > > just now that
> > > my reply wasn't sent.
> > > The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or
>
> > > not.
> > > The vhost thread utilized less than 100% (of the other cpu) when
> polling
> > > was disabled.
> > > Enabling polling increased its utilization to 100% (in which case both
>
> > > cpus were 100% utilized).
> >
> > Hmm this means the testing wasn't successful then, as you said:
> >
> > The idea was to get it 100% loaded, so we can see that the polling is
> > getting it to produce higher throughput.
> >
> > in fact here you are producing more throughput but spending more power
> > to produce it, which can have any number of explanations besides polling
> > improving the efficiency. For example, increasing system load might
> > disable host power management.
> >
>
> Hi Michael,
> I re-ran the tests, this time with the "turbo mode" and "C-states"
> features off.
> No Polling:
> 1 VM running netperf (msg size 64B): 1107 Mbits/sec
> Polling:
> 1 VM running netperf (msg size 64B): 1572 Mbits/sec
>
>
>
>
>
>
>
> As you can see from the new results, the numbers are lower,
> but relatively (polling on/off) there's no change.
> Thank you,
> Razya

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.

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> >
> > > > --
> > > > MST
> > > >
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