netdev - Re: arm: Optimization for ethernet MAC handling at91

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Date:	Tue, 12 Jan 2010 19:08:19 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	James Kosin <JKosin@...comgrp.com>
CC:	linux-kernel@...r.kernel.org,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: arm: Optimization for ethernet MAC handling at91_ether.c

Le 12/01/2010 18:51, James Kosin a écrit :
> On 1/12/2010 11:40 AM, Eric Dumazet wrote:

>> If this happens once in a while, why do you want driver to retry the transmit ?
> 
> (a)  It would improve performance by allowing the ISR to handle the re-transmit in this case.
> (b)  It would help in the case of small glitches that may happen from external SDRAM without taxing the polling required to handle the re-transmit of the packet... ie: overhead required to re-queue and initiate a packet delivery... since the packet is already scheduled for delivery now.
> 

OK, but then this also adds an extra check for each tx completion.

I dont have this piece of hardware, but seeing it has a one skb tx queue (!),
I suppose TX performance is not very good anyway...


at91ether_interrupt() should probably handle tx completion before rx, to feed
next frame faster.

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