netdev - Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.

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Date:	Wed, 25 Mar 2009 18:51:56 +0100
From:	Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>
To:	avorontsov@...mvista.com
Cc:	leoli@...escale.com,
	'linuxppc-dev Development' <linuxppc-dev@...abs.org>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.

Anton Vorontsov <avorontsov@...mvista.com> wrote on 25/03/2009 15:25:40:
> On Wed, Mar 25, 2009 at 02:30:49PM +0100, Joakim Tjernlund wrote:
> > >>From 1c2f23b1f37f4818c0fd0217b93eb38ab6564840 Mon Sep 17 00:00:00 
2001
> > From: Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>
> > Date: Tue, 24 Mar 2009 10:19:27 +0100
> > Subject: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
> >  Also increase NAPI weight somewhat.
> >  This will make the system alot more responsive while
> >  ping flooding the ucc_geth ethernet interaface.
> 
> Some time ago I've tried a similar thing for this driver, but during
> tcp (or udp I don't quite remember) netperf tests I was getting tx
> watchdog timeouts after ~2-5 minutes of work. I was testing with a
> gigabit and 100 Mbit link, with 100 Mbit link the issue was not
> reproducible.
> 
> Though, I recalling I was doing a bit more than your patch: I was
> also clearing the TX events in the ucce register before calling
> ucc_geth_tx, that way I was trying to avoid stale interrupts. That
> helped to increase an overall performance (not only responsiveness),
> but as I said my approach didn't pass the tests.
> 
> I don't really think that your patch may cause this, but can you
> try netperf w/ this patch applied anyway? And see if it really
> doesn't cause any issues under stress?

Does the line(in ucc_geth_tx()) look OK to you:
        if ((bd == ugeth->txBd[txQ]) && (netif_queue_stopped(dev) == 0))
                        break;

Sure does look fishy to me.
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