Re: Preallocated skb's?

From: Robert Olsson (Robert.Olsson@data.slu.se)
Date: Thu Sep 14 2000 - 10:50:51 EST


Yes !

The FF experiments with 2.1.X indicated improvement factor about 2-3 times
with skb recycling. With combination of FF and skb recycling we could reach
fast Ethernet wire speed forwarding on 400 Mhz CPU. About ~147 KPPS.
As jamal reported the improvement is much less today but the forwarding
performance is impressive even without FF and skb recycling. Slab seems
to do a good job and especially when the debug is disabled. :-)

                                                --ro

Andi Kleen writes:
> On Thu, Sep 14, 2000 at 11:59:32PM +1100, Andrew Morton wrote:
> > That's 20 usec per interrupt, of which 1 usec could be saved by skb
> > pooling.
>
> FF usually runs with interrupt mitigation at higher rates (8-16 or even
> more packets / interrupt). I agree though that it probably does not
> make too much difference. alloc_skb could probably be made cheaper
> for the FF case by being more clever in the slab constructor (I think
> there was some bitrot during 2.3 on the cache line usage -- 2.2 pretty
> much only needed 2 cache lines in the header for a FF packet)
>
>
> -Andi
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