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authorEric Dumazet <edumazet@google.com>2014-09-24 04:11:22 -0700
committerDavid S. Miller <davem@davemloft.net>2014-09-28 16:36:48 -0400
commitcd7d8498c9a5d510c64db38d9f4f4fbc41790f09 (patch)
tree4057e715ca8227a081db71f1ec1359011c5c1a00 /net/ipv4/tcp.c
parentdc83d4d8f6c897022c974a00769b7a6efee6aed8 (diff)
downloadop-kernel-dev-cd7d8498c9a5d510c64db38d9f4f4fbc41790f09.zip
op-kernel-dev-cd7d8498c9a5d510c64db38d9f4f4fbc41790f09.tar.gz
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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp.c')
-rw-r--r--net/ipv4/tcp.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 553b01f..87289e5 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -963,7 +963,7 @@ new_segment:
skb->ip_summed = CHECKSUM_PARTIAL;
tp->write_seq += copy;
TCP_SKB_CB(skb)->end_seq += copy;
- skb_shinfo(skb)->gso_segs = 0;
+ tcp_skb_pcount_set(skb, 0);
if (!copied)
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
@@ -1261,7 +1261,7 @@ new_segment:
tp->write_seq += copy;
TCP_SKB_CB(skb)->end_seq += copy;
- skb_shinfo(skb)->gso_segs = 0;
+ tcp_skb_pcount_set(skb, 0);
from += copy;
copied += copy;
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