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Re: NAPI-ized tulip patch against 2.4.20-rc1

To: Robert Olsson <Robert.Olsson@xxxxxxxxxxx>
Subject: Re: NAPI-ized tulip patch against 2.4.20-rc1
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Wed, 06 Nov 2002 13:30:56 -0800
Cc: "'netdev@xxxxxxxxxxx'" <netdev@xxxxxxxxxxx>
Organization: Candela Technologies
References: <3DC8B85B.5050805@candelatech.com> <15817.21170.173913.829498@robur.slu.se> <3DC95631.6030001@candelatech.com> <15817.29109.859144.565330@robur.slu.se>
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Robert Olsson wrote:
Ben Greear writes:

I still doubt ;-)

With e1000 I played with various settings for RX-buffers rather recently when the 82544 increased the number of available buffers from 256 to 4096.

And I guess my test looks a bit like yours... Injecting an "overload" of packets. I found was 256 buffers was the optimum. Approximative of course.

It's possible that it is a particular issue with my NICs (Old Phobos 4-port). Phobos folks said the bridge chipset has errata that make it un-suitable for high speeds. And something about a memory divide-by-four error. It may be that the extra buffers help hide the hardware defects in some manner. I was, for instance, seeing cases where packets just dissappeared...and no error counters were being bumped.

With the latest kernel drivers, the 570tx NIC seems to have
trouble autonegotiating full-duplex again, so I have not been testing
with it lately (I think it uses the same bridge chipset anyway.)

I will try changing around those numbers again now that I have a baseline
to work from.

And as you saw for SMP with recycle it is easy to feed the recycled skb back to CPU were it was created/processed.

Yes, I can see how that would be useful on SMP, so there may be less gain for single-proc systems. I actually am pretty fuzzy on cache-line optimizations and the like...


Thanks, Ben

--
Ben Greear <greearb@xxxxxxxxxxxxxxx>       <Ben_Greear AT excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear



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