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Date: Fri, 18 Aug 2006 14:23:56 -0500
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 2/4]: powerpc/cell spidernet low watermark patch.
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From: linas@austin.ibm.com (Linas Vepstas)
Cc: Arnd Bergmann <arnd@arndb.de>, netdev@vger.kernel.org,
	James K Lewis <jklewis@us.ibm.com>, linux-kernel@vger.kernel.org,
	linuxppc-dev@ozlabs.org, Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
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On Thu, Aug 17, 2006 at 01:43:40AM +0200, Benjamin Herrenschmidt wrote:
> 
> Sounds good (without actually looking at the code though :), that was a
> long required improvement to that driver. Also, we should probably look
> into using NAPI polling for tx completion queue as well, no ?

Just for a lark, I tried using NAPI polling, while disabling all TX
interrupts. Performance was a disaster: 8Mbits/sec, fom which I conclude
that the tcp ack packets do not flow back fast enough to allw reliance
on NAPI polling for transmit.

I was able to get as high as 960 Mbits/sec in unusal circumstances, 
at 100% cpu usage. Oprofile indicates that the next major improvement
would be to add scatter/gather, which I'll take a shot at next week,
if I don't get interrupted. However, I'm getting interrupted a lot these
days.

--linas