Re: RFC: NAPI packet weighting patch

[Eric Dumazet <dada1@xxxxxxxxxxxxx>]

David S. Miller a écrit :

> 2) As shown above, it gives you compute time which can be used to
>    schedule the prefetch.  This nearly makes RX replenishment free.
>    Instead of having the CPU spin on a cache miss when we run
>    eth_type_trans() during those cycles, we do useful work.
>
> I'm going to play around with these ideas in the tg3 driver.
> Obvious patch below.

Then maybe we could also play with prefetchw() in the case the incoming frame
is small enough to be copied to a new skb.

drivers/net/tg3.c

        copy_skb = dev_alloc_skb(len + 2);
        if (copy_skb == NULL)
                goto drop_it_no_recycle;
+       prefetchw(copy_skb->data);

        copy_skb->dev = tp->dev;
        skb_reserve(copy_skb, 2);
        skb_put(copy_skb, len);