Messages in this thread | | | Date | Wed, 26 May 1999 22:17:55 +0200 (MEST) | From | Finn Arne Gangstad <> | Subject | Re: [patch] checksum P6 asm buffer overflow fix + 686 improvements |
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On Mon, 24 May 1999, Andrea Arcangeli wrote:
> I also improved a bit the asm (mainly the csum_copy that wasn't > unrolling enough according to the new numbers).
Unrolling more eats more instruction cache for incredibly low gain, I don't think it's a good idea except maybe for dedicated routers. As for the other changes, such as changing testl %esi,%esi to clc, that hurts the current code (we spent a LOT of time putting the right instructions in there, and got some very non-obvious results a lot of times, due to alignment issues and other PPro weirdness I guess).
I also noticed that you removed the code that handles 2-byte aligned areas, I don't think that's a very good idea, all the adcl instructions will probably slow down a lot if they don't operate on aligned data.
If there is interesting in improving the checksum codes, I can try to dig out my old test program which let you benchmark with various "real-life" packet sizes with both warm and cold i-cache and d-cache.
- Finn Arne
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