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Merge master.kernel.org:/pub/scm/linux/kernel/git/acme/net-2.6
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David S. Miller committed Dec 4, 2006
2 parents b4ad86b + 2bbf29a commit 83ac58b
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Showing 4 changed files with 237 additions and 139 deletions.
33 changes: 33 additions & 0 deletions net/dccp/ccids/Kconfig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,4 +89,37 @@ config IP_DCCP_CCID3_DEBUG
parameter to 0 or 1.

If in doubt, say N.

config IP_DCCP_CCID3_RTO
int "Use higher bound for nofeedback timer"
default 100
depends on IP_DCCP_CCID3 && EXPERIMENTAL
---help---
Use higher lower bound for nofeedback timer expiration.

The TFRC nofeedback timer normally expires after the maximum of 4
RTTs and twice the current send interval (RFC 3448, 4.3). On LANs
with a small RTT this can mean a high processing load and reduced
performance, since then the nofeedback timer is triggered very
frequently.

This option enables to set a higher lower bound for the nofeedback
value. Values in units of milliseconds can be set here.

A value of 0 disables this feature by enforcing the value specified
in RFC 3448. The following values have been suggested as bounds for
experimental use:
* 16-20ms to match the typical multimedia inter-frame interval
* 100ms as a reasonable compromise [default]
* 1000ms corresponds to the lower TCP RTO bound (RFC 2988, 2.4)

The default of 100ms is a compromise between a large value for
efficient DCCP implementations, and a small value to avoid disrupting
the network in times of congestion.

The purpose of the nofeedback timer is to slow DCCP down when there
is serious network congestion: experimenting with larger values should
therefore not be performed on WANs.


endmenu
119 changes: 65 additions & 54 deletions net/dccp/ccids/ccid3.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -121,21 +121,23 @@ static inline void ccid3_update_send_time(struct ccid3_hc_tx_sock *hctx)
/*
* Update X by
* If (p > 0)
* x_calc = calcX(s, R, p);
* X_calc = calcX(s, R, p);
* X = max(min(X_calc, 2 * X_recv), s / t_mbi);
* Else
* If (now - tld >= R)
* X = max(min(2 * X, 2 * X_recv), s / R);
* tld = now;
*
* If X has changed, we also update the scheduled send time t_now,
* the inter-packet interval t_ipi, and the delta value.
*/
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;

/* To avoid large error in calcX */
if (hctx->ccid3hctx_p >= TFRC_SMALLEST_P) {
if (hctx->ccid3hctx_p > 0) {
hctx->ccid3hctx_x_calc = tfrc_calc_x(hctx->ccid3hctx_s,
hctx->ccid3hctx_rtt,
hctx->ccid3hctx_p);
Expand Down Expand Up @@ -223,16 +225,14 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
ccid3_tx_state_name(hctx->ccid3hctx_state));
/* Halve sending rate */

/* If (X_calc > 2 * X_recv)
/* If (p == 0 || X_calc > 2 * X_recv)
* X_recv = max(X_recv / 2, s / (2 * t_mbi));
* Else
* X_recv = X_calc / 4;
*/
BUG_ON(hctx->ccid3hctx_p >= TFRC_SMALLEST_P &&
hctx->ccid3hctx_x_calc == 0);
BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);

/* check also if p is zero -> x_calc is infinity? */
if (hctx->ccid3hctx_p < TFRC_SMALLEST_P ||
if (hctx->ccid3hctx_p == 0 ||
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_T_MBI));
Expand All @@ -245,9 +245,10 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
}
/*
* Schedule no feedback timer to expire in
* max(4 * R, 2 * s/X) = max(4 * R, 2 * t_ipi)
* max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi)
* See comments in packet_recv() regarding the value of t_RTO.
*/
t_nfb = max(4 * hctx->ccid3hctx_rtt, 2 * hctx->ccid3hctx_t_ipi);
t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
break;
case TFRC_SSTATE_NO_SENT:
DCCP_BUG("Illegal %s state NO_SENT, sk=%p", dccp_role(sk), sk);
Expand Down Expand Up @@ -338,7 +339,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
* else
* // send the packet in (t_nom - t_now) milliseconds.
*/
if (delay >= hctx->ccid3hctx_delta)
if (delay - (long)hctx->ccid3hctx_delta >= 0)
return delay / 1000L;
break;
case TFRC_SSTATE_TERM:
Expand Down Expand Up @@ -412,10 +413,8 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
struct dccp_tx_hist_entry *packet;
struct timeval now;
unsigned long t_nfb;
u32 t_elapsed;
u32 pinv;
u32 x_recv;
u32 r_sample;
long r_sample, t_elapsed;

BUG_ON(hctx == NULL);

Expand All @@ -426,31 +425,44 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)

opt_recv = &hctx->ccid3hctx_options_received;

t_elapsed = dp->dccps_options_received.dccpor_elapsed_time * 10;
x_recv = opt_recv->ccid3or_receive_rate;
pinv = opt_recv->ccid3or_loss_event_rate;

switch (hctx->ccid3hctx_state) {
case TFRC_SSTATE_NO_FBACK:
case TFRC_SSTATE_FBACK:
/* Calculate new round trip sample by
* R_sample = (now - t_recvdata) - t_delay */
/* get t_recvdata from history */
/* get packet from history to look up t_recvdata */
packet = dccp_tx_hist_find_entry(&hctx->ccid3hctx_hist,
DCCP_SKB_CB(skb)->dccpd_ack_seq);
if (unlikely(packet == NULL)) {
DCCP_WARN("%s, sk=%p, seqno %llu(%s) does't exist "
DCCP_WARN("%s(%p), seqno %llu(%s) doesn't exist "
"in history!\n", dccp_role(sk), sk,
(unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type));
return;
}

/* Update RTT */
/* Update receive rate */
hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;

/* Update loss event rate */
pinv = opt_recv->ccid3or_loss_event_rate;
if (pinv == ~0U || pinv == 0)
hctx->ccid3hctx_p = 0;
else
hctx->ccid3hctx_p = 1000000 / pinv;

dccp_timestamp(sk, &now);
r_sample = timeval_delta(&now, &packet->dccphtx_tstamp);
if (unlikely(r_sample <= t_elapsed))
DCCP_WARN("r_sample=%uus,t_elapsed=%uus\n",

/*
* Calculate new round trip sample as per [RFC 3448, 4.3] by
* R_sample = (now - t_recvdata) - t_elapsed
*/
r_sample = timeval_delta(&now, &packet->dccphtx_tstamp);
t_elapsed = dp->dccps_options_received.dccpor_elapsed_time * 10;

if (unlikely(r_sample <= 0)) {
DCCP_WARN("WARNING: R_sample (%ld) <= 0!\n", r_sample);
r_sample = 0;
} else if (unlikely(r_sample <= t_elapsed))
DCCP_WARN("WARNING: r_sample=%ldus <= t_elapsed=%ldus\n",
r_sample, t_elapsed);
else
r_sample -= t_elapsed;
Expand All @@ -473,31 +485,25 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
hctx->ccid3hctx_t_ld = now;

ccid3_update_send_time(hctx);
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
} 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,
hctx->ccid3hctx_rtt, r_sample);
ccid3_pr_debug("%s(%p), s=%u, w_init=%u, "
"R_sample=%ldus, X=%u\n", dccp_role(sk),
sk, hctx->ccid3hctx_s, w_init, r_sample,
hctx->ccid3hctx_x);

/* Update receive rate */
hctx->ccid3hctx_x_recv = x_recv;/* X_recv in bytes per sec */
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
} else {
hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt +
(u32)r_sample ) / 10;

/* Update loss event rate */
if (pinv == ~0 || pinv == 0)
hctx->ccid3hctx_p = 0;
else {
hctx->ccid3hctx_p = 1000000 / pinv;
ccid3_hc_tx_update_x(sk, &now);

if (hctx->ccid3hctx_p < TFRC_SMALLEST_P) {
hctx->ccid3hctx_p = TFRC_SMALLEST_P;
ccid3_pr_debug("%s, sk=%p, Smallest p used!\n",
dccp_role(sk), sk);
}
ccid3_pr_debug("%s(%p), RTT=%uus (sample=%ldus), s=%u, "
"p=%u, X_calc=%u, X=%u\n", dccp_role(sk),
sk, hctx->ccid3hctx_rtt, r_sample,
hctx->ccid3hctx_s, hctx->ccid3hctx_p,
hctx->ccid3hctx_x_calc,
hctx->ccid3hctx_x);
}

/* unschedule no feedback timer */
Expand All @@ -512,16 +518,20 @@ 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). */
/*
* Update timeout interval for the nofeedback timer.
* We use a configuration option to increase the lower bound.
* This can help avoid triggering the nofeedback timer too often
* ('spinning') on LANs with small RTTs.
*/
hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt,
USEC_PER_SEC );
CONFIG_IP_DCCP_CCID3_RTO *
(USEC_PER_SEC/1000) );
/*
* Schedule no feedback timer to expire in
* max(4 * R, 2 * s/X) = max(4 * R, 2 * t_ipi)
* max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi)
*/
t_nfb = max(4 * hctx->ccid3hctx_rtt, 2 * hctx->ccid3hctx_t_ipi);
t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);

ccid3_pr_debug("%s, sk=%p, Scheduled no feedback timer to "
"expire in %lu jiffies (%luus)\n",
Expand All @@ -535,7 +545,8 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
hctx->ccid3hctx_idle = 1;
break;
case TFRC_SSTATE_NO_SENT:
DCCP_WARN("Illegal ACK received - no packet has been sent\n");
if (dccp_sk(sk)->dccps_role == DCCP_ROLE_CLIENT)
DCCP_WARN("Illegal ACK received - no packet sent\n");
/* fall through */
case TFRC_SSTATE_TERM: /* ignore feedback when closing */
break;
Expand Down
2 changes: 0 additions & 2 deletions net/dccp/ccids/ccid3.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,8 +51,6 @@
/* Parameter t_mbi from [RFC 3448, 4.3]: backoff interval in seconds */
#define TFRC_T_MBI 64

#define TFRC_SMALLEST_P 40

enum ccid3_options {
TFRC_OPT_LOSS_EVENT_RATE = 192,
TFRC_OPT_LOSS_INTERVALS = 193,
Expand Down
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