On 12/7/05, David S. Miller <[EMAIL PROTECTED]> wrote: > From: Eric Dumazet <[EMAIL PROTECTED]> > Date: Thu, 08 Dec 2005 04:47:05 +0100 > > > #4#5 as proposed in the patch can not be a win > > > > + prefetch(next_skb); > > + prefetch(next_skb->data - NET_IP_ALIGN); > > > > because at the time #5 is done, the CPU dont have in its cache > > next_skb->data > > (because the #4 prefetch is the previous instruction) > > > > prefetch(ptr) is mostly a free hint for the CPU. > > > > prefetch(*ptr) can be expensive because of the needed indirection that might > > slow down the CPU if *ptr is not yet available in its L1 cache. > > Agreed. Doing a depdant prefetch back to back so close like > that is nearly pointless.
right, after i did this code, i realized that, and it is demonstrable that #4 hurts, if only a little. I'm sticking with my suggestion we go to #1,#2,#5 - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
