On Fri, 2012-10-05 at 14:22 +0200, Eric Dumazet wrote: > Yes, but the idea of the patch was to _avoid_ next pskb_expand_head() > calls...
yes but we cannot be sure of that, the caller may not have a good idea of the headroom needed for the whole lifetime of the skb it's better to think we will reduce number of calls, not avoid them that's why I think doubling the size each time is dangerous, since we silently request bigger and bigger allocations if an skb takes an unoptimized path > Hmm, > > this changes nothing assuming current_end == skb_end_offset(skb) > and current_head = skb->head My idea was to leave skb->end at its last position even if we grow skb->head. Since we have a way to know the current allocation size of skb->head, further pskb_expand_head() calls to request tailroom would just push skb->tail & skb->end together if that fits in current ksize(). I've not looked at recent changes in mainline, since you changed how skb->head is managed, that may be totally impossible. Your proposed changed API change to expand_head will fill this anyway. > New convention would be : pass number of needed bytes after current > tail, not after current end. Fully agree on this -- Maxime -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
