netdev - Re: [v3 RFC PATCH 0/4] Implement multiqueue virtio-net

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Message-ID: <OFBE9E2C99.648EFB19-ON652577C8.0035FEDD-652577C8.0036AD51@in.ibm.com>
Date:	Tue, 26 Oct 2010 15:31:39 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	anthony@...emonkey.ws, arnd@...db.de, avi@...hat.com,
	davem@...emloft.net, eric.dumazet@...il.com, kvm@...r.kernel.org,
	netdev@...r.kernel.org, netdev-owner@...r.kernel.org,
	rusty@...tcorp.com.au
Subject: Re: [v3 RFC PATCH 0/4] Implement multiqueue virtio-net

> "Michael S. Tsirkin" <mst@...hat.com>
>
> On Tue, Oct 26, 2010 at 02:38:53PM +0530, Krishna Kumar2 wrote:
> > Results for UDP BW tests (unidirectional, sum across
> > 3 iterations, each iteration of 45 seconds, default
> > netperf, vhosts bound to cpus 0-3; no other tuning):
>
> Is binding vhost threads to CPUs really required?
> What happens if we let the scheduler do its job?

Nothing drastic, I remember BW% and SD% both improved a
bit as a result of binding. I started binding vhost thread
after Avi suggested it in response to my v1 patch (he
suggested some more that I haven't done), and have been
doing only this tuning ever since. This is part of his
mail for the tuning:

> 		 vhost:
> 		 		 thread #0:  CPU0
> 		 		 thread #1:  CPU1
> 		 		 thread #2:  CPU2
> 		 		 thread #3:  CPU3

I simply bound each thread to CPU0-3 instead.

Thanks,

- KK

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