From: Andrea Bittau Date: Tue, 19 Sep 2006 20:14:43 +0000 (-0700) Subject: [DCCP] CCID2: Halve cwnd once upon multiple losses in a single RTT X-Git-Tag: v2.6.19-rc1~1272^2~50 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=374bcf32c86e1b56eab832bbb6b21e636707eab6;p=linux-2.6 [DCCP] CCID2: Halve cwnd once upon multiple losses in a single RTT When multiple losses occur in one RTT, the window should be halved only once [a single "congestion event"]. This is now implemented, although not perfectly. Slightly changed the interface for changing the cwnd: pass hctx instead of dp. This is required in order to allow for change_cwnd to be called from _init(). Signed-off-by: Andrea Bittau Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller --- diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c index 93a30ae8d0..b88da03586 100644 --- a/net/dccp/ccids/ccid2.c +++ b/net/dccp/ccids/ccid2.c @@ -187,10 +187,8 @@ static void ccid2_change_l_ack_ratio(struct sock *sk, int val) dp->dccps_l_ack_ratio = val; } -static void ccid2_change_cwnd(struct sock *sk, int val) +static void ccid2_change_cwnd(struct ccid2_hc_tx_sock *hctx, int val) { - struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk); - if (val == 0) val = 1; @@ -234,7 +232,7 @@ static void ccid2_hc_tx_rto_expire(unsigned long data) hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd >> 1; if (hctx->ccid2hctx_ssthresh < 2) hctx->ccid2hctx_ssthresh = 2; - ccid2_change_cwnd(sk, 1); + ccid2_change_cwnd(hctx, 1); /* clear state about stuff we sent */ hctx->ccid2hctx_seqt = hctx->ccid2hctx_seqh; @@ -444,7 +442,7 @@ static inline void ccid2_new_ack(struct sock *sk, /* increase every 2 acks */ hctx->ccid2hctx_ssacks++; if (hctx->ccid2hctx_ssacks == 2) { - ccid2_change_cwnd(sk, hctx->ccid2hctx_cwnd + 1); + ccid2_change_cwnd(hctx, hctx->ccid2hctx_cwnd+1); hctx->ccid2hctx_ssacks = 0; *maxincr = *maxincr - 1; } @@ -457,7 +455,7 @@ static inline void ccid2_new_ack(struct sock *sk, hctx->ccid2hctx_acks++; if (hctx->ccid2hctx_acks >= hctx->ccid2hctx_cwnd) { - ccid2_change_cwnd(sk, hctx->ccid2hctx_cwnd + 1); + ccid2_change_cwnd(hctx, hctx->ccid2hctx_cwnd + 1); hctx->ccid2hctx_acks = 0; } } @@ -532,6 +530,22 @@ static void ccid2_hc_tx_dec_pipe(struct sock *sk) ccid2_hc_tx_kill_rto_timer(sk); } +static void ccid2_congestion_event(struct ccid2_hc_tx_sock *hctx, + struct ccid2_seq *seqp) +{ + if (time_before(seqp->ccid2s_sent, hctx->ccid2hctx_last_cong)) { + ccid2_pr_debug("Multiple losses in an RTT---treating as one\n"); + return; + } + + hctx->ccid2hctx_last_cong = jiffies; + + ccid2_change_cwnd(hctx, hctx->ccid2hctx_cwnd >> 1); + hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd; + if (hctx->ccid2hctx_ssthresh < 2) + hctx->ccid2hctx_ssthresh = 2; +} + static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) { struct dccp_sock *dp = dccp_sk(sk); @@ -542,7 +556,6 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) unsigned char veclen; int offset = 0; int done = 0; - int loss = 0; unsigned int maxincr = 0; ccid2_hc_tx_check_sanity(hctx); @@ -636,7 +649,8 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) !seqp->ccid2s_acked) { if (state == DCCP_ACKVEC_STATE_ECN_MARKED) { - loss = 1; + ccid2_congestion_event(hctx, + seqp); } else ccid2_new_ack(sk, seqp, &maxincr); @@ -688,7 +702,13 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) /* check for lost packets */ while (1) { if (!seqp->ccid2s_acked) { - loss = 1; + ccid2_pr_debug("Packet lost: %llu\n", + seqp->ccid2s_seq); + /* XXX need to traverse from tail -> head in + * order to detect multiple congestion events in + * one ack vector. + */ + ccid2_congestion_event(hctx, seqp); ccid2_hc_tx_dec_pipe(sk); } if (seqp == hctx->ccid2hctx_seqt) @@ -707,14 +727,6 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) hctx->ccid2hctx_seqt = hctx->ccid2hctx_seqt->ccid2s_next; } - if (loss) { - /* XXX do bit shifts guarantee a 0 as the new bit? */ - ccid2_change_cwnd(sk, hctx->ccid2hctx_cwnd >> 1); - hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd; - if (hctx->ccid2hctx_ssthresh < 2) - hctx->ccid2hctx_ssthresh = 2; - } - ccid2_hc_tx_check_sanity(hctx); } @@ -722,7 +734,7 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk) { struct ccid2_hc_tx_sock *hctx = ccid_priv(ccid); - hctx->ccid2hctx_cwnd = 1; + ccid2_change_cwnd(hctx, 1); /* Initialize ssthresh to infinity. This means that we will exit the * initial slow-start after the first packet loss. This is what we * want. @@ -741,6 +753,7 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk) hctx->ccid2hctx_rttvar = -1; hctx->ccid2hctx_lastrtt = 0; hctx->ccid2hctx_rpdupack = -1; + hctx->ccid2hctx_last_cong = jiffies; hctx->ccid2hctx_rtotimer.function = &ccid2_hc_tx_rto_expire; hctx->ccid2hctx_rtotimer.data = (unsigned long)sk; diff --git a/net/dccp/ccids/ccid2.h b/net/dccp/ccids/ccid2.h index 2a02ce04ba..5b2ef4acb3 100644 --- a/net/dccp/ccids/ccid2.h +++ b/net/dccp/ccids/ccid2.h @@ -71,6 +71,7 @@ struct ccid2_hc_tx_sock { u64 ccid2hctx_rpseq; int ccid2hctx_rpdupack; int ccid2hctx_sendwait; + unsigned long ccid2hctx_last_cong; }; struct ccid2_hc_rx_sock {