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 --- net/ipv4/tcp_minisocks.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'net') diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 6b5c64f3c925..706932726a11 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -387,8 +387,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, /* Now setup tcp_sock */ newtp = tcp_sk(newsk); newtp->pred_flags = 0; - newtp->rcv_nxt = treq->rcv_isn + 1; - newtp->snd_nxt = newtp->snd_una = newtp->snd_sml = treq->snt_isn + 1; + newtp->rcv_wup = newtp->copied_seq = newtp->rcv_nxt = treq->rcv_isn + 1; + newtp->snd_sml = newtp->snd_una = newtp->snd_nxt = treq->snt_isn + 1; tcp_prequeue_init(newtp); @@ -422,10 +422,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, tcp_set_ca_state(newsk, TCP_CA_Open); tcp_init_xmit_timers(newsk); skb_queue_head_init(&newtp->out_of_order_queue); - newtp->rcv_wup = treq->rcv_isn + 1; newtp->write_seq = treq->snt_isn + 1; newtp->pushed_seq = newtp->write_seq; - newtp->copied_seq = treq->rcv_isn + 1; newtp->rx_opt.saw_tstamp = 0; -- cgit v1.2.3