linux-kernel - Re: [PATCH] virtio-ring: Use threshold for switching to indirect descriptors

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Date:	Wed, 30 Nov 2011 18:17:22 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
	markmc@...hat.com
Subject: Re: [PATCH] virtio-ring: Use threshold for switching to indirect
 descriptors

Sorry, I forgot to copy-paste one of the results :)

On Wed, 2011-11-30 at 18:11 +0200, Sasha Levin wrote:
> I did some testing of indirect descriptors under different workloads.
> 
> All tests were on a 2 vcpu guest with vhost on. Simple TCP_STREAM using
> netperf.
> 
> Indirect desc off:
> guest -> host, 1 stream: ~4600mb/s
> host -> guest, 1 stream: ~5900mb/s
> guest -> host, 8 streams: ~620mb/s (on average)
> host -> guest, 8 stream: ~600mb/s (on average)
> 
> Indirect desc on:
> guest -> host, 1 stream: ~4900mb/s
> host -> guest, 1 stream: ~5400mb/s
> guest -> host, 8 streams: ~620mb/s (on average)
> host -> guest, 8 stream: ~600mb/s (on average)
Should be:
host -> guest, 8 stream: ~515mb/s (on average)

> 
> Which means that for one stream, guest to host gets faster while host to
> guest gets slower when indirect descriptors are on.
> 

-- 

Sasha.

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