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[DCCP] CCID2: Halve cwnd once upon multiple losses in a single RTT

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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>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Andrea Bittau 2006-09-19 13:14:43 -07:00 committed by David S. Miller
parent 07978aabd5
commit 374bcf32c8
2 changed files with 32 additions and 18 deletions
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49
net/dccp/ccids/ccid2.c
View file

@ -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;

1
net/dccp/ccids/ccid2.h
View file

@ -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 {