netdev - Re: Network performance with small packets

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Date:	Wed, 02 Feb 2011 07:39:45 -0800
From:	Shirley Ma <mashirle@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Krishna Kumar2 <krkumar2@...ibm.com>,
	David Miller <davem@...emloft.net>, kvm@...r.kernel.org,
	mashirle@...ux.vnet.ibm.com, netdev@...r.kernel.org,
	netdev-owner@...r.kernel.org, Sridhar Samudrala <sri@...ibm.com>,
	Steve Dobbelstein <steved@...ibm.com>
Subject: Re: Network performance with small packets

On Wed, 2011-02-02 at 12:48 +0200, Michael S. Tsirkin wrote:
> Yes, I think doing this in the host is much simpler,
> just send an interrupt after there's a decent amount
> of space in the queue.
> 
> Having said that the simple heuristic that I coded
> might be a bit too simple.

>>From the debugging out what I have seen so far (a single small message
TCP_STEAM test), I think the right approach is to patch both guest and
vhost. The problem I have found is a regression for single  small
message TCP_STEAM test. Old kernel works well for TCP_STREAM, only new
kernel has problem.

For Steven's problem, it's multiple stream TCP_RR issues, the old guest
doesn't perform well, so does new guest kernel. We tested reducing vhost
signaling patch before, it didn't help the performance at all.

Thanks
Shirley

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