Anton Vorontsov [off-list ref] wrote on 25/03/2009 15:25:40:

On Wed, Mar 25, 2009 at 02:30:49PM +0100, Joakim Tjernlund wrote:

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From 1c2f23b1f37f4818c0fd0217b93eb38ab6564840 Mon Sep 17 00:00:00 

2001

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From: Joakim Tjernlund <redacted>
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.