Re: [PATCH] vhost: Add polling mode

"Michael S. Tsirkin" [off-list ref] wrote on 20/08/2014 01:57:10 PM:

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Results:

Netperf, 1 vm:
The polling patch improved throughput by ~33% (1516 MB/sec -> 2046 

MB/sec).

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Number of exits/sec decreased 6x.
The same improvement was shown when I tested with 3 vms running 

netperf

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(4086 MB/sec -> 5545 MB/sec).

filebench, 1 vm:
ops/sec improved by 13% with the polling patch. Number of exits 

was reduced by

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31%.
The same experiment with 3 vms running filebench showed similar 

numbers.

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Signed-off-by: Razya Ladelsky <redacted>

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