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

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Date:	Wed, 25 Mar 2009 17:25:40 +0300
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
Cc:	Netdev <netdev@...r.kernel.org>, leoli@...escale.com,
	'linuxppc-dev Development' <linuxppc-dev@...abs.org>
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.

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?

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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