From 54287cc178cf85dbae0decec8b4dc190bff757ad Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 22 Feb 2007 03:20:44 -0800 Subject: [TCP]: Keep copied_seq, rcv_wup and rcv_next together. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit I noticed in oprofile study a cache miss in tcp_rcv_established() to read copied_seq. ffffffff80400a80 : /* tcp_rcv_established total: 4034293   2.0400 */  55493  0.0281 :ffffffff80400bc9:   mov    0x4c8(%r12),%eax copied_seq 543103  0.2746 :ffffffff80400bd1:   cmp    0x3e0(%r12),%eax   rcv_nxt     if (tp->copied_seq == tp->rcv_nxt &&         len - tcp_header_len <= tp->ucopy.len) { In this function, the cache line 0x4c0 -> 0x500 is used only for this reading 'copied_seq' field. rcv_wup and copied_seq should be next to rcv_nxt field, to lower number of active cache lines in hot paths. (tcp_rcv_established(), tcp_poll(), ...) As you suggested, I changed tcp_create_openreq_child() so that these fields are changed together, to avoid adding a new store buffer stall. Patch is 64bit friendly (no new hole because of alignment constraints) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/tcp.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/tcp.h') diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 29d3089038a..415193e171e 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -242,6 +242,8 @@ struct tcp_sock { * See RFC793 and RFC1122. The RFC writes these in capitals. */ u32 rcv_nxt; /* What we want to receive next */ + u32 copied_seq; /* Head of yet unread data */ + u32 rcv_wup; /* rcv_nxt on last window update sent */ u32 snd_nxt; /* Next sequence we send */ u32 snd_una; /* First byte we want an ack for */ @@ -307,10 +309,8 @@ struct tcp_sock { struct sk_buff_head out_of_order_queue; /* Out of order segments go here */ u32 rcv_wnd; /* Current receiver window */ - u32 rcv_wup; /* rcv_nxt on last window update sent */ u32 write_seq; /* Tail(+1) of data held in tcp send buffer */ u32 pushed_seq; /* Last pushed seq, required to talk to windows */ - u32 copied_seq; /* Head of yet unread data */ /* SACKs data */ struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */ -- cgit v1.2.3