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| author | Eric Dumazet <dada1@cosmosbay.com> | 2007-02-22 03:20:44 -0800 |
|---|---|---|
| committer | David S. Miller <davem@sunset.davemloft.net> | 2007-04-25 22:23:21 -0700 |
| commit | 54287cc178cf85dbae0decec8b4dc190bff757ad (patch) | |
| tree | 44dedf7be5ac37fae65718d359ff598902247753 /net/ipv4/tcp_minisocks.c | |
| parent | cf4c6bf83d0fa070f60b1ba8124dfe0e65fbfbcc (diff) | |
| download | lwn-54287cc178cf85dbae0decec8b4dc190bff757ad.tar.gz lwn-54287cc178cf85dbae0decec8b4dc190bff757ad.zip | |
[TCP]: Keep copied_seq, rcv_wup and rcv_next together.
I noticed in oprofile study a cache miss in tcp_rcv_established() to read
copied_seq.
ffffffff80400a80 <tcp_rcv_established>: /* 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 <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_minisocks.c')
| -rw-r--r-- | net/ipv4/tcp_minisocks.c | 6 |
1 files changed, 2 insertions, 4 deletions
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; |