On Tue, 20 Aug 2013 18:24:57 +0200 Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > On Tue, 2013-08-20 at 09:20 -0700, Stephen Hemminger wrote: > > > All code must check for needed headroom first, and copy packet > > if space is not available. Since excess headroom is always safe, > > most devices just always use the same worst case headroom. > > > > Even with your changes this will still be necessary since packets will > > be still in flight while features change. > > I agree, it will always be necessary. I guess the question boils down to > whether/what N bytes headroom more or less actually make a difference. > > The wireless stack currently sets needed_headroom to 34 or so I think, > but I will need to increase by 8 which was why I had this question to > start with. However, those 34 are an absolute worst case - in most cases > it's much less... > > So I suppose the other question we should ask is will increasing from > ~34 to ~42 make a significant different that it's worth thinking about > avoiding it in the common cases at all? > > johannes > The only thing that might matter is alignment. but +/- 8 bytes isn't going to change that. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
