netdev - Re: optimizations to sk_buff handling in rds_tcp_data

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Date:	Sat, 9 Apr 2016 20:18:53 -0400
From:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: optimizations to sk_buff handling in rds_tcp_data_ready

On (04/07/16 07:16), Eric Dumazet wrote:
> Use skb split like TCP in output path ?
> Really, pskb_expand_head() is not supposed to copy payload ;)

Question- how come skb_split doesnt have to deal with frag_list
and do a skb_walk_frags()? Couldn't the split-line be somewhere
in the frag_list? Also even for the skb_split_inside_header,
dont we have to set
  skb_shinfo(skb1)->frag_list = skb_shinfo(skb)->frag_list;
and cut loose the skb_shinfo(skb)->frag_list?

As I try to mimic skb_split in some new set of "skb_carve"
funtions, I'm running into all  the various frag_list cases. I'm 
afraid I might end up needing most of the stuff under the "Pure 
masohism" (sic) comment in __pskb_pull_tail(). 

--Sowmini