From patchwork Sat Sep 20 17:52:32 2008 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [net-next,14/15] tcp: don't clear lost_skb_hint when not necessary Date: Sat, 20 Sep 2008 07:52:32 -0000 From: =?utf-8?q?Ilpo_J=C3=A4rvinen?= X-Patchwork-Id: 732 Message-Id: <1221933153-11874-15-git-send-email-ilpo.jarvinen@helsinki.fi> To: David Miller Cc: netdev@vger.kernel.org, "=?utf-8?q?Ilpo=20J=E4rvinen?=" Most importantly avoid doing it with cumulative ACK. However, since we have lost_cnt_hint in the picture as well needing adjustments, it's not as trivial as dealing with retransmit_skb_hint (and cannot be done in the all place we could trivially leave retransmit_skb_hint untouched). With the previous patch, this should mostly remove O(n^2) behavior while cumulative ACKs start flowing once rexmit after a lossy round-trip made it through. Signed-off-by: Ilpo Järvinen --- net/ipv4/tcp_input.c | 14 +++++++++++++- 1 files changed, 13 insertions(+), 1 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f217b4f..9daeb07 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2844,6 +2844,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) int flag = 0; u32 pkts_acked = 0; u32 reord = tp->packets_out; + u32 prior_sacked = tp->sacked_out; s32 seq_rtt = -1; s32 ca_seq_rtt = -1; ktime_t last_ackt = net_invalid_timestamp(); @@ -2925,9 +2926,11 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) tcp_unlink_write_queue(skb, sk); sk_wmem_free_skb(sk, skb); - tcp_clear_retrans_hints_partial(tp); + tp->scoreboard_skb_hint = NULL; if (skb == tp->retransmit_skb_hint) tp->retransmit_skb_hint = NULL; + if (skb == tp->lost_skb_hint) + tp->lost_skb_hint = NULL; } if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) @@ -2946,6 +2949,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) /* Non-retransmitted hole got filled? That's reordering */ if (reord < prior_fackets) tcp_update_reordering(sk, tp->fackets_out - reord, 0); + + /* No need to care for underflows here because + * the lost_skb_hint gets NULLed if we're past it + * (or something non-trivial happened) + */ + if (tcp_is_fack(tp)) + tp->lost_cnt_hint -= pkts_acked; + else + tp->lost_cnt_hint -= prior_sacked - tp->sacked_out; } tp->fackets_out -= min(pkts_acked, tp->fackets_out);