From ad971f616aa98ea2503f1a1064637bfb4ef7b21e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 11 Oct 2014 15:17:29 -0700 Subject: [PATCH] tcp: fix tcp_ack() performance problem We worked hard to improve tcp_ack() performance, by not accessing skb_shinfo() in fast path (cd7d8498c9a5 tcp: change tcp_skb_pcount() location) We still have one spurious access because of ACK timestamping, added in commit e1c8a607b281 ("net-timestamp: ACK timestamp for bytestreams") By checking if sk_tsflags has SOF_TIMESTAMPING_TX_ACK set, we can avoid two cache line misses for the common case. While we are at it, add two prefetchw() : One in tcp_ack() to bring skb at the head of write queue. One in tcp_clean_rtx_queue() loop to bring following skb, as we will delete skb from the write queue and dirty skb->next->prev. Add a couple of [un]likely() clauses. After this patch, tcp_ack() is no longer the most consuming function in tcp stack. Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Cc: Neal Cardwell Cc: Yuchung Cheng Cc: Van Jacobson Signed-off-by: David S. Miller --- Reading git-format-patch failed