From: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
To: dccp@vger.kernel.org
Subject: [PATCH 08/11] CCID2: Halve cwnd once upon multiple losses in a single RTT
Date: Thu, 22 Jun 2006 17:58:21 +0000 [thread overview]
Message-ID: <20060622175821.GH4230@shorty.sorbonet.org> (raw)
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 <a.bittau@cs.ucl.ac.uk>
---
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index b2d140f..f0bc0b6 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -188,10 +188,8 @@ static void ccid2_change_l_ack_ratio(str
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;
@@ -235,7 +233,7 @@ static void ccid2_hc_tx_rto_expire(unsig
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;
@@ -445,7 +443,7 @@ static inline void ccid2_new_ack(struct
/* 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;
}
@@ -458,7 +456,7 @@ static inline void ccid2_new_ack(struct
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;
}
}
@@ -534,6 +532,22 @@ static void ccid2_hc_tx_dec_pipe(struct
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)) {
+ dccp_pr_debug("Multiple losses in one 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);
@@ -544,7 +558,6 @@ static void ccid2_hc_tx_packet_recv(stru
unsigned char veclen;
int offset = 0;
int done = 0;
- int loss = 0;
unsigned int maxincr = 0;
ccid2_hc_tx_check_sanity(hctx);
@@ -638,7 +651,8 @@ static void ccid2_hc_tx_packet_recv(stru
!seqp->ccid2s_acked) {
if (state =
DCCP_ACKVEC_STATE_ECN_MARKED) {
- loss = 1;
+ ccid2_congestion_event(hctx,
+ seqp);
} else
ccid2_new_ack(sk, seqp,
&maxincr);
@@ -690,7 +704,13 @@ static void ccid2_hc_tx_packet_recv(stru
/* 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)
@@ -709,14 +729,6 @@ static void ccid2_hc_tx_packet_recv(stru
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);
}
@@ -724,7 +736,7 @@ static int ccid2_hc_tx_init(struct ccid
{
struct ccid2_hc_tx_sock *hctx = ccid_priv(ccid);
- hctx->ccid2hctx_cwnd = 1;
+ ccid2_change_cwnd(hctx, 1);
hctx->ccid2hctx_ssthresh = 666666; /* "infinite" [for a while] */
hctx->ccid2hctx_numdupack = 3;
hctx->ccid2hctx_seqbufc = 0;
@@ -739,6 +751,7 @@ static int ccid2_hc_tx_init(struct ccid
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 1a7904e..3bc4b76 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 {
reply other threads:[~2006-06-22 17:58 UTC|newest]
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