Re: [PATCH]: 1st step to remove skb_linearize() in ip6_tables.c and optimization

[Patrick McHardy <kaber@trash.net>]

Harald Welte wrote:
> On Thu, Jun 24, 2004 at 01:26:10PM +0200, Patrick McHardy wrote:
> 
>>One call to skb_linearize would most likely be less expensive. I'm
>>thinking about putting the copied protocol header in the control
>>buffer, this would reduce this extensive copying a lot. We could also
>>do some common preprocessing steps in one place, like converting
>>things to host byte order.
> 
> 
> yes, it would be only one copy... but to real memory..
> Maybe we need some benchmarking on this.

It may be only to cache, but in case the skb is non-linear skb_copy_bits
calls local_bh_disable and kmap_atomic for the paged part, and walks
frag_list. I don't expect skb_ip_make_writable to be much faster in
all cases, but a new function which would only linearize the transport
headers, without copying the entire skb, probably would be.
Unfortunately I don't have time to implement and benchmark it right now.

>>Regards
>>Patrick
> 
>