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On Thu, 14 Sep 2000, David S. Miller wrote:

> Date: Thu, 14 Sep 2000 04:44:53 -0400
> From: Jeff Garzik <>
> Does anyone think that allocating skbs during system idle time
> would be useful?
> I really don't like these sorts of things, because it makes an
> assumption as to what memory is about to be used for.
> What if you were to preallocate skbs while idle, then the next thing
> which happens is some userland program walks over a 2gb dataset and
> no network activity happens at all.

The FF code of the tulip does have skb recycling code.
And i belive Jes' acenic code does or did at some point.
Robert Olson and I were thinking of taking out that code out of the
tulip for reasons such as you talk about (and the thought maybe that
the per-CPU slab might have obsoleted that requirement). We did some tests
with 2.4.0-test7 and were suprised to observe that at high rate of input
packets, it still made as a big a difference as 7000 packets per second
;-> i.e we got 7Kpps more by using skb recycling.

Dave, would a scheme with an aging of the skbs in the recycle queue
and an upper bound of the number of packets sitting on the queue be
Maybe ANK can make a comment as well.
Robert and I plan to play with such a scheme for a long time under many
different scenarios and come with numbers (throughput etc) instead of
"here's a patch and intuitively it makes sense".
This is really a 2.5 thing if acceptable.


PS:- OLS patch coming soon; a few more tests (as time permits);->

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