Re: [PATCH 2/4]: powerpc/cell spidernet low watermark patch.

From: Linas Vepstas
Date: Fri Aug 18 2006 - 15:21:29 EST

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

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