From: Eric Dumazet Date: Wed, 24 Sep 2014 11:11:22 +0000 (-0700) Subject: tcp: change tcp_skb_pcount() location X-Git-Tag: fixes-against-v3.18-rc2~144^2~132 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cd7d8498c9a5d510c64db38d9f4f4fbc41790f09;p=pandora-kernel.git tcp: change tcp_skb_pcount() location Our goal is to access no more than one cache line access per skb in a write or receive queue when doing the various walks. After recent TCP_SKB_CB() reorganizations, it is almost done. Last part is tcp_skb_pcount() which currently uses skb_shinfo(skb)->gso_segs, which is a terrible choice, because it needs 3 cache lines in current kernel (skb->head, skb->end, and shinfo->gso_segs are all in 3 different cache lines, far from skb->cb) This very simple patch reuses space currently taken by tcp_tw_isn only in input path, as tcp_skb_pcount is only needed for skb stored in write queue. This considerably speeds up tcp_ack(), granted we avoid shinfo->tx_flags to get SKBTX_ACK_TSTAMP, which seems possible. This also speeds up all sack processing in general. This speeds up tcp_sendmsg() because it no longer has to access/dirty shinfo. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- Reading git-diff-tree failed