netdev - Re: Network performance with small packets

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Message-ID: <1296595955.26937.822.camel@localhost.localdomain>
Date:	Tue, 01 Feb 2011 13:32:35 -0800
From:	Shirley Ma <mashirle@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Sridhar Samudrala <sri@...ibm.com>,
	Steve Dobbelstein <steved@...ibm.com>,
	David Miller <davem@...emloft.net>, kvm@...r.kernel.org,
	mashirle@...ux.vnet.ibm.com, netdev@...r.kernel.org
Subject: Re: Network performance with small packets

On Tue, 2011-02-01 at 23:24 +0200, Michael S. Tsirkin wrote:
> My theory is that the issue is not signalling.
> Rather, our queue fills up, then host handles
> one packet and sends an interrupt, and we
> immediately wake the queue. So the vq
> once it gets full, stays full.

>>From the printk debugging output, it might not be exactly the case. The
ring gets full, run a bit, then gets full, then run a bit, then full...

> If you try my patch with bufs threshold set to e.g.
> half the vq, what we will do is send interrupt after we have processed
> half the vq.  So host has half the vq to go, and guest has half the vq
> to fill.
> 
> See?

I am cleaning up my set up to run your patch ...

Shirley


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