Re: New net features for added performance

From: Werner Almesberger (
Date: Sun Feb 25 2001 - 07:22:49 EST

Jeff Garzik wrote:
> 1) Rx Skb recycling.

Sounds like a potentially useful idea. To solve the most immediate memory
pressure problems, maybe VM could provide some function that does a kfree
in cases of memory shortage, and that does nothing otherwise, so the
driver could offer to free the skb after netif_rx. You still need to go
over the list in idle periods, though.

> 2) Tx packet grouping.

Hmm, I think we need an estimate of how long a packet train you'd usually
get. A flag looks reasonably inexpensive. Estimated numbers sound like

> Disadvantages? Can this sort of knowledge be obtained by a netdevice
> right now, without any kernel modifications?

Question is what the hardware really needs. If you can change the
interrupt point easily, it's probably cheapest to do all the work in

> 3) Slabbier packet allocation.

Hmm, this may actually be worse during bursts: if you burst exceeds
the preallocated size, you have to perform more expensive/slower
operations (e.g. running a tasklet) to refill your cache.

- Werner

 / Werner Almesberger, ICA, EPFL, CH  /
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Wed Feb 28 2001 - 21:00:09 EST