Re: [PATCH] vhost: Add polling mode

Razya Ladelsky
2014-08-21T14:23:55Z

"Michael S. Tsirkin" <mst@redhat.com> wrote on 20/08/2014 01:57:10 PM:

> > Results:
> >
> > Netperf, 1 vm:
> > The polling patch improved throughput by ~33% (1516 MB/sec -> 2046
MB/sec).
> > Number of exits/sec decreased 6x.
> > The same improvement was shown when I tested with 3 vms running
netperf
> > (4086 MB/sec -> 5545 MB/sec).
> >
> > filebench, 1 vm:
> > ops/sec improved by 13% with the polling patch. Number of exits
> was reduced by
> > 31%.
> > The same experiment with 3 vms running filebench showed similar
numbers.
> >
> > Signed-off-by: Razya Ladelsky <razya@il.ibm.com>
>
> This really needs more thourough benchmarking report, including
> system data. One good example for a related patch:
> http://lwn.net/Articles/551179/
> though for virtualization, we need data about host as well, and if you
> want to look at streaming benchmarks, you need to test different message
> sizes and measure packet size.
>

Hi Michael,
I have already tried running netperf with several message sizes:
64,128,256,512,600,800...
But the results are inconsistent even in the baseline/unpatched
configuration.
For smaller msg sizes, I get consistent numbers. However, at some point,
when I increase the msg size
I get unstable results. For example, for a 512B msg, I get two scenarios:
vm utilization 100%, vhost utilization 75%, throughput ~6300
vm utilization 80%, vhost utilization 13%, throughput ~9400 (line rate)

I don't know why vhost is behaving that way for certain message sizes.
Do you have any insight to why this is happening?
Thank you,
Razya