Re: [PATCH] vhost: Add polling mode

Razya Ladelsky
2014-08-17T12:35:39Z

> >
> > 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

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