Re: mac80211 truesize bugs

[Herbert Xu <herbert@gondor.apana.org.au>]

On Sun, May 04, 2008 at 04:08:36AM +0200, Johannes Berg wrote:
>
> So, what is mac80211 supposed to do? It needs up to 54 bytes of
> available headroom (for an encrypted mesh packet which currently can't
> really happen, but anyway) yet it cannot pskb_expand_head() either.
> Cloning each packet seems even more expensive, and just like skb_orphan
> subverts the purpose of the socket accounting.

If all/the majority of your packets need the space then put it in
LL_MAX_HEADER.  In any case, you should always expand the packet
if necessary in your output routine since LL_MAX_HEADER is just a
hint.  Yes cloning is expensive compared to not having to do it,
but as long as this is only done for the exception then it's
irrelevant.

Cheers,
-- 
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