Messages in this thread |  | | | Date | Sat, 24 Feb 2001 19:03:38 -0500 | | From | Jeff Garzik <> | | Subject | Re: New net features for added performance |
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Andi Kleen wrote: > > Jeff Garzik <jgarzik@mandrakesoft.com> writes: > > > Advantages: A de-allocation immediately followed by a reallocation is > > eliminated, less L1 cache pollution during interrupt handling. > > Potentially less DMA traffic between card and host. > > > > Disadvantages? > > You need a new mechanism to cope with low memory situations because the > drivers can tie up quite a bit of memory (in fact you gave up unified > memory management).
I think you misunderstand.. netif_rx frees the skb. In this example:
netif_rx(skb); /* free skb of size PKT_BUF_SZ */ skb = dev_alloc_skb(PKT_BUF_SZ) an alloc of a PKT_BUF_SZ'd skb immediately follows a free of a same-sized skb. 100% of the time.
It seems an obvious shortcut to me, to have __netif_rx or similar -clear- the skb head not free it. No changes to memory management or additional low memory situations created by this, AFAICS.
> 4) Better support for aligned RX by only copying the header, no the whole > packet, to end up with an aligned IP header. Unless the driver knows about > all protocol lengths this means the stack needs to support "parse header > in this buffer, then switch to other buffer with computed offset for data"
This requires scatter-gather hardware support, right? If so, would this support only exist for checksumming hardware -- like the current zerocopy -- or would non-checksumming SG hardware like tulip be supported too?
Jeff
-- Jeff Garzik | "You see, in this world there's two kinds of Building 1024 | people, my friend: Those with loaded guns MandrakeSoft | and those who dig. You dig." --Blondie - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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