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RE: [Xen-devel] Increase txqueuelen of vif devices

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>, Keir Fraser <keir@xxxxxxx>, Miroslav Rezanina <mrezanin@xxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Increase txqueuelen of vif devices
From: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
Date: Mon, 25 Oct 2010 10:07:20 +0100
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Thread-topic: [Xen-devel] Increase txqueuelen of vif devices
I was wondering about the short queues the other day. They definitely cause 
problems with short packet workloads and the suspicion is that the shortness is 
largely historical.
I plan to work on a new netback receive side (moving the grant copy into the 
guest) shortly, but I have some other stuff to get through before I can make a 
proper start. Hope to have something in a few weeks though.

  Paul

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of James Harper
> Sent: 23 October 2010 00:26
> To: Keir Fraser; Miroslav Rezanina; xen-devel
> Subject: RE: [Xen-devel] Increase txqueuelen of vif devices
> 
> >
> > The expectation was that domU would push enough receive buffers to
> dom0 to
> > avoid packet loss. The txqueuelen is just a fallback for that.
> Still,
> yeah,
> > it could be increased if it improves perf given default domU
> netfront
> > behaviour.
> >
> 
> I have found the ring a bit small when trying to cope with many
> small
> buffers, but it's workload and system dependent so it should
> probably be
> set on a case by case basis.
> 
> Are there any disadvantages to increasing the txqueue?
> 
> What ever happened to the new netchannel stuff? Did that promise
> larger
> rings?
> 
> James
> 
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