Re: [PATCH 4/7] mac80211: make ieee80211_get_hdrlen_from_skb return unsigned

Harvey Harrison
2008-06-09T16:25:03Z

On Mon, 2008-06-09 at 11:15 +0200, Johannes Berg wrote:
> > unlikely() isn't some magic make-me-faster function, it just moves
> > code
> > to the end of the function to get it out of the icache and jumps to it
> > in the unlikely case it is taken. When all there is is a return, I
> > don't think it even makes any difference. In both these cases a
> > comment
> > is probably more appropriate.
>
> That's not true on ppc where you can actually tell the processor about
> the jump likelyhood for its branch prediction.

I was unaware of that.

>
> > On X86-32 at least the generated code is exactly the same with or
> > without the unlikely()s. I'll put them back in a follow-on if people
> > are really attached to them.
>
> Please keep them there, I think they make sense for normal operation.

Kept, will be in a v2.

Harvey