linux-kernel - Re: [RFC] net: napi fix

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Message-ID: <20071213141441.GB3806@ff.dom.local>
Date:	Thu, 13 Dec 2007 15:14:41 +0100
From:	Jarek Poplawski <jarkao2@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	auke-jan.h.kok@...el.com, gallatin@...i.com, joonwpark81@...il.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	jgarzik@...ox.com, shemminger@...ux-foundation.org,
	jesse.brandeburg@...el.com
Subject: Re: [RFC] net: napi fix

On Thu, Dec 13, 2007 at 05:50:13AM -0800, David Miller wrote:
> From: Jarek Poplawski <jarkao2@...il.com>
> Date: Thu, 13 Dec 2007 14:49:53 +0100
> 
> > As a matter of fact, since it's "unlikely()" in net_rx_action() anyway,
> > I wonder what is the main reason or gain of leaving such a tricky
> > exception, instead of letting drivers to always decide which is the
> > best moment for napi_complete()? (Or maybe even, in such a case, they
> > should call some function with this list_move_tail() if it's so
> > useful?)
> 
> It is the only sane way to synchronize the list manipulations.
> 
> There has to be a way for ->poll() to tell net_rx_action() two things:
> 
> 1) How much work was completed, so we can adjust 'budget'
> 2) Was the NAPI quota exhausted?  So that we know that
>    net_rx_action() still "owns" the polling context and
>    thus can do the list manipulation safely.
> 
> And these both need to be encoded into one single return value, thus
> the adopted convention that "work == weight" means that the device has
> not done a NAPI complete.

Thanks! So, I've to rethink this all...

Jarek P.
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