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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2006-11-28 19:51:42 -0200
committerDavid S. Miller <davem@sunset.davemloft.net>2006-12-02 21:31:01 -0800
commita79ef76f4d8424324c2f108824a7398571193f43 (patch)
treea80e84d19c867e1432fc05ae50199487ce2ea2b2 /net/dccp/ccids
parent841bac1d607d8bf2e068e4b24393fb77372814e3 (diff)
[DCCP] ccid3: Larger initial windows
This implements the larger-initial-windows feature for CCID 3, as described in section 5 of RFC 4342. When the first feedback packet arrives, the sender can send up to 2..4 packets per RTT, instead of just one. The patch further * reduces the number of timestamping calls by passing the timestamp value (which is computed in one of the calling functions anyway) as argument * renames one constant with a very long name into one which is shorter and resembles the one in RFC 3448 (t_mbi) * simplifies some of the min_t/max_t cases where both `x', `y' have the same type Commiter note: renamed TFRC_t_mbi to TFRC_T_MBI, to follow Linux coding style. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Diffstat (limited to 'net/dccp/ccids')
-rw-r--r--net/dccp/ccids/ccid3.c66
-rw-r--r--net/dccp/ccids/ccid3.h4
2 files changed, 37 insertions, 33 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 05513f3df65..aa5440ee20a 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -128,7 +128,8 @@ static inline void ccid3_update_send_time(struct ccid3_hc_tx_sock *hctx)
* X = max(min(2 * X, 2 * X_recv), s / R);
* tld = now;
*/
-static void ccid3_hc_tx_update_x(struct sock *sk)
+static void ccid3_hc_tx_update_x(struct sock *sk, struct timeval *now)
+
{
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
const __u32 old_x = hctx->ccid3hctx_x;
@@ -138,23 +139,20 @@ static void ccid3_hc_tx_update_x(struct sock *sk)
hctx->ccid3hctx_x_calc = tfrc_calc_x(hctx->ccid3hctx_s,
hctx->ccid3hctx_rtt,
hctx->ccid3hctx_p);
- hctx->ccid3hctx_x = max_t(u32, min_t(u32, hctx->ccid3hctx_x_calc,
- 2 * hctx->ccid3hctx_x_recv),
- (hctx->ccid3hctx_s /
- TFRC_MAX_BACK_OFF_TIME));
- } else {
- struct timeval now;
+ hctx->ccid3hctx_x = max_t(u32, min(hctx->ccid3hctx_x_calc,
+ hctx->ccid3hctx_x_recv * 2),
+ hctx->ccid3hctx_s / TFRC_T_MBI);
+
+ } else if (timeval_delta(now, &hctx->ccid3hctx_t_ld) >=
+ hctx->ccid3hctx_rtt) {
+ hctx->ccid3hctx_x = max(min(hctx->ccid3hctx_x_recv,
+ hctx->ccid3hctx_x ) * 2,
+ usecs_div(hctx->ccid3hctx_s,
+ hctx->ccid3hctx_rtt) );
+ hctx->ccid3hctx_t_ld = *now;
+ } else
+ ccid3_pr_debug("Not changing X\n");
- dccp_timestamp(sk, &now);
- if (timeval_delta(&now, &hctx->ccid3hctx_t_ld) >=
- hctx->ccid3hctx_rtt) {
- hctx->ccid3hctx_x = max_t(u32, min_t(u32, hctx->ccid3hctx_x_recv,
- hctx->ccid3hctx_x) * 2,
- usecs_div(hctx->ccid3hctx_s,
- hctx->ccid3hctx_rtt));
- hctx->ccid3hctx_t_ld = now;
- }
- }
if (hctx->ccid3hctx_x != old_x)
ccid3_update_send_time(hctx);
}
@@ -196,12 +194,9 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
switch (hctx->ccid3hctx_state) {
case TFRC_SSTATE_NO_FBACK:
- /* Halve send rate */
- hctx->ccid3hctx_x /= 2;
- if (hctx->ccid3hctx_x < (hctx->ccid3hctx_s /
- TFRC_MAX_BACK_OFF_TIME))
- hctx->ccid3hctx_x = (hctx->ccid3hctx_s /
- TFRC_MAX_BACK_OFF_TIME);
+ /* RFC 3448, 4.4: Halve send rate directly */
+ hctx->ccid3hctx_x = min_t(u32, hctx->ccid3hctx_x / 2,
+ hctx->ccid3hctx_s / TFRC_T_MBI);
ccid3_pr_debug("%s, sk=%p, state=%s, updated tx rate to %d "
"bytes/s\n",
@@ -221,6 +216,8 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
if (!hctx->ccid3hctx_idle ||
(hctx->ccid3hctx_x_recv >=
4 * usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_rtt))) {
+ struct timeval now;
+
ccid3_pr_debug("%s, sk=%p, state=%s, not idle\n",
dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state));
@@ -238,12 +235,13 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
if (hctx->ccid3hctx_p < TFRC_SMALLEST_P ||
hctx->ccid3hctx_x_calc > 2 * hctx->ccid3hctx_x_recv)
hctx->ccid3hctx_x_recv = max_t(u32, hctx->ccid3hctx_x_recv / 2,
- hctx->ccid3hctx_s / (2 * TFRC_MAX_BACK_OFF_TIME));
+ hctx->ccid3hctx_s / (2 * TFRC_T_MBI));
else
hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc / 4;
/* Update sending rate */
- ccid3_hc_tx_update_x(sk);
+ dccp_timestamp(sk, &now);
+ ccid3_hc_tx_update_x(sk, &now);
}
/*
* Schedule no feedback timer to expire in
@@ -473,11 +471,21 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
* q is a constant, RFC 3448 recomments 0.9
*/
if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
+ /* Use Larger Initial Windows [RFC 4342, sec. 5]
+ * We deviate in that we use `s' instead of `MSS'. */
+ u16 w_init = max( 4 * hctx->ccid3hctx_s,
+ max(2 * hctx->ccid3hctx_s, 4380));
+ hctx->ccid3hctx_rtt = r_sample;
+ hctx->ccid3hctx_x = usecs_div(w_init, r_sample);
+ hctx->ccid3hctx_t_ld = now;
+
+ ccid3_update_send_time(hctx);
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
- hctx->ccid3hctx_rtt = r_sample;
- } else
+ } else {
hctx->ccid3hctx_rtt = (hctx->ccid3hctx_rtt * 9) / 10 +
r_sample / 10;
+ ccid3_hc_tx_update_x(sk, &now);
+ }
ccid3_pr_debug("%s, sk=%p, New RTT estimate=%uus, "
"r_sample=%us\n", dccp_role(sk), sk,
@@ -502,9 +510,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
/* unschedule no feedback timer */
sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
- /* Update sending rate (and likely t_ipi, t_nom, and delta) */
- ccid3_hc_tx_update_x(sk);
-
/* remove all packets older than the one acked from history */
dccp_tx_hist_purge_older(ccid3_tx_hist,
&hctx->ccid3hctx_hist, packet);
@@ -514,7 +519,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
*/
sk->sk_write_space(sk);
-
/* Update timeout interval. We use the alternative variant of
* [RFC 3448, 3.1] which sets the upper bound of t_rto to one
* second, as it is suggested for TCP (see RFC 2988, 2.4). */
diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h
index dbb884426df..27cb20ae1da 100644
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -48,8 +48,8 @@
/* In usecs - half the scheduling granularity as per RFC3448 4.6 */
#define TFRC_OPSYS_HALF_TIME_GRAN (USEC_PER_SEC / (2 * HZ))
-/* In seconds */
-#define TFRC_MAX_BACK_OFF_TIME 64
+/* Parameter t_mbi from [RFC 3448, 4.3]: backoff interval in seconds */
+#define TFRC_T_MBI 64
#define TFRC_SMALLEST_P 40