Re: NS83820 2.6.0-test5 driver seems unstable on IA64

From: David S. Miller <davem_at_redhat.com>
Date: 2003-09-26 11:12:58
On Thu, 25 Sep 2003 20:11:27 +0400
Ivan Kokshaysky <ink@jurassic.park.msu.ru> wrote:

> On Alpha it is - I did some experimentation yesterday with
> the tulip driver and "rx_copybreak=0" vs default "rx_copybreak=1518".
> That's true, copying the large packet is very expensive due to constant
> cache misses. On UP1500 it costs more than 2500 cycles per 1.5Kb
> copy on large ftp transfers.
> OTOH, minimal time to handle unaligned load is ~200 cycles (ev6 cpu),
> but only when the trap handler itself and its data are in L1 cache
> (like doing unaligned load in a tight loop). In the real life average
> time is ~400 cycles due to cache misses.
> Further, with "rx_copybreak=0" I've got 20 (!) unaligned traps per TCP
> packet, i.e. penalty was 8000 vs 2500 cycles...

Fine, then we should have something like an rx_copybreak scheme in
the ns83820 driver too.

Thanks for your data.
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Received on Thu Sep 25 21:26:37 2003

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