netdev - Re: [Xen-devel] [RFC PATCH 3/6] netback: switch to NAPI + kthread model

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Date:	Mon, 16 Jan 2012 10:49:38 +0000
From:	Wei Liu <wei.liu2@...rix.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
CC:	<wei.liu2@...rix.com>, David Vrabel <david.vrabel@...rix.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [Xen-devel] [RFC PATCH 3/6] netback: switch to NAPI + kthread
 model

On Mon, 2012-01-16 at 10:45 +0000, Ian Campbell wrote:
> On Mon, 2012-01-16 at 09:33 +0000, Wei Liu (Intern) wrote:
> > On Fri, 2012-01-13 at 18:21 +0000, David Vrabel wrote:
> > > On 13/01/12 16:59, Wei Liu wrote:
> > > > This patch implements 1:1 model netback. We utilizes NAPI and kthread
> > > > to do the weight-lifting job:
> > > > 
> > > >   - NAPI is used for guest side TX (host side RX)
> > > >   - kthread is used for guest side RX (host side TX)
> > > > 
> > > > This model provides better scheduling fairness among vifs. It also
> > > > lays the foundation for future work.
> > > > 
> > > > The major defect for the current implementation is that in the NAPI
> > > > poll handler we don't actually disable interrupt. Xen stuff is
> > > > different from real hardware, it requires some other tuning of ring
> > > > macros.
> > > 
> > > RING_FINAL_CHECK_FOR_REQUESTS() looks it does the correct thing to me.
> > > 
> > > David
> > 
> > I need to stop the other end from generating events, so
> > RING_FINAL_CHECK_FOR_REQUESTS is not the right answer I think.
> 
> What you need is a variant which sets req_event some large distance into
> the future instead of to just req_cons + 1. Or possibly it should be set
> to just in the past (e.g. req_cons - 1). Call it something like
> RING_POLL_FOR_REQUESTS().
> 

Seems like a right direction. Will try this.


Wei.

> Ian.
> 
> > 
> > 
> > Wei.
> > 
> 
> 


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