[CCID3]: Introduce usecs_div
To avoid open coding this all over the place.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 60e3a5f..ff41977 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -40,6 +40,15 @@
#include "../packet_history.h"
#include "ccid3.h"
+/*
+ * Reason for maths with 10 here is to avoid 32 bit overflow when a is big.
+ */
+static inline u32 usecs_div(const u32 a, const u32 b)
+{
+ const u32 tmp = a * (USEC_PER_SEC / 10);
+ return b > 20 ? tmp / (b / 10) : tmp;
+}
+
#ifdef CCID3_DEBUG
extern int ccid3_debug;
@@ -748,20 +757,13 @@
/* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */
static inline void ccid3_calc_new_t_ipi(struct ccid3_hc_tx_sock *hctx)
{
- if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK)
- return;
- /* if no feedback spec says t_ipi is 1 second (set elsewhere and then
- * doubles after every no feedback timer (separate function) */
-
- if (hctx->ccid3hctx_x < 10) {
- ccid3_pr_debug("ccid3_calc_new_t_ipi - ccid3hctx_x < 10\n");
- hctx->ccid3hctx_x = 10;
- }
- hctx->ccid3hctx_t_ipi = (hctx->ccid3hctx_s * 100000)
- / (hctx->ccid3hctx_x / 10);
- /* reason for above maths with 10 in there is to avoid 32 bit
- * overflow for jumbo packets */
-
+ /*
+ * If no feedback spec says t_ipi is 1 second (set elsewhere and then
+ * doubles after every no feedback timer (separate function)
+ */
+ if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
+ hctx->ccid3hctx_t_ipi = usecs_div(hctx->ccid3hctx_s,
+ hctx->ccid3hctx_x);
}
/* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
@@ -769,7 +771,6 @@
{
hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,
TFRC_OPSYS_HALF_TIME_GRAN);
-
}
/*
@@ -802,22 +803,13 @@
do_gettimeofday(&now);
if (timeval_delta(&now, &hctx->ccid3hctx_t_ld) >=
hctx->ccid3hctx_rtt) {
- /* Avoid divide by zero below */
- const u32 rtt = max_t(u32, hctx->ccid3hctx_rtt, 10);
-
- hctx->ccid3hctx_x = max_t(u32, min_t(u32, 2 * hctx->ccid3hctx_x_recv,
- 2 * hctx->ccid3hctx_x),
- ((hctx->ccid3hctx_s * 100000) /
- (rtt / 10)));
- /* Using 100000 and 10 to avoid 32 bit overflow for jumbo frames */
+ 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 == 0) {
- ccid3_pr_debug("ccid3hctx_x = 0!\n");
- hctx->ccid3hctx_x = 1;
- }
}
static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
@@ -826,7 +818,6 @@
struct dccp_sock *dp = dccp_sk(sk);
unsigned long next_tmout = 0;
struct ccid3_hc_tx_sock *hctx = dp->dccps_hc_tx_ccid_private;
- u32 rtt;
bh_lock_sock(sk);
if (sock_owned_by_user(sk)) {
@@ -840,19 +831,14 @@
ccid3_pr_debug("%s, sk=%p, state=%s\n", dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state));
- if (hctx->ccid3hctx_x < 10) {
- ccid3_pr_debug("TFRC_SSTATE_NO_FBACK ccid3hctx_x < 10\n");
- hctx->ccid3hctx_x = 10;
- }
-
switch (hctx->ccid3hctx_state) {
case TFRC_SSTATE_TERM:
goto out;
case TFRC_SSTATE_NO_FBACK:
/* Halve send rate */
hctx->ccid3hctx_x /= 2;
- if (hctx->ccid3hctx_x <
- (hctx->ccid3hctx_s / TFRC_MAX_BACK_OFF_TIME))
+ if (hctx->ccid3hctx_x < (hctx->ccid3hctx_s /
+ TFRC_MAX_BACK_OFF_TIME))
hctx->ccid3hctx_x = (hctx->ccid3hctx_s /
TFRC_MAX_BACK_OFF_TIME);
@@ -861,9 +847,9 @@
dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state),
hctx->ccid3hctx_x);
- next_tmout = max_t(u32, 2 * (hctx->ccid3hctx_s * 100000) / (hctx->ccid3hctx_x / 10),
+ next_tmout = max_t(u32, 2 * usecs_div(hctx->ccid3hctx_s,
+ hctx->ccid3hctx_x),
TFRC_INITIAL_TIMEOUT);
- /* do above maths with 100000 and 10 to prevent overflow on 32 bit */
/*
* FIXME - not sure above calculation is correct. See section
* 5 of CCID3 11 should adjust tx_t_ipi and double that to
@@ -875,12 +861,9 @@
* Check if IDLE since last timeout and recv rate is less than
* 4 packets per RTT
*/
- rtt = hctx->ccid3hctx_rtt;
- if (rtt < 10)
- rtt = 10;
- /* stop divide by zero below */
if (!hctx->ccid3hctx_idle ||
- (hctx->ccid3hctx_x_recv >= 4 * (hctx->ccid3hctx_s * 100000) / (rtt / 10))) {
+ (hctx->ccid3hctx_x_recv >=
+ 4 * usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_rtt))) {
ccid3_pr_debug("%s, sk=%p, state=%s, not idle\n",
dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state));
@@ -905,13 +888,13 @@
/* Update sending rate */
ccid3_hc_tx_update_x(sk);
}
- if (hctx->ccid3hctx_x == 0) {
- ccid3_pr_debug("TFRC_SSTATE_FBACK ccid3hctx_x = 0!\n");
- hctx->ccid3hctx_x = 10;
- }
- /* Schedule no feedback timer to expire in max(4 * R, 2 * s / X) */
+ /*
+ * Schedule no feedback timer to expire in
+ * max(4 * R, 2 * s / X)
+ */
next_tmout = max_t(u32, hctx->ccid3hctx_t_rto,
- 2 * (hctx->ccid3hctx_s * 100000) / (hctx->ccid3hctx_x / 10));
+ 2 * usecs_div(hctx->ccid3hctx_s,
+ hctx->ccid3hctx_x));
break;
default:
printk(KERN_CRIT "%s: %s, sk=%p, Illegal state (%d)!\n",
@@ -1053,8 +1036,10 @@
* Algorithm in "8.1. Window Counter Valuer" in
* draft-ietf-dccp-ccid3-11.txt
*/
- quarter_rtt = timeval_delta(&now, &hctx->ccid3hctx_t_last_win_count) /
- (hctx->ccid3hctx_rtt / 4);
+ quarter_rtt = timeval_delta(&now, &hctx->ccid3hctx_t_last_win_count);
+ if (likely(hctx->ccid3hctx_rtt > 8))
+ quarter_rtt /= hctx->ccid3hctx_rtt / 4;
+
if (quarter_rtt > 0) {
hctx->ccid3hctx_t_last_win_count = now;
hctx->ccid3hctx_last_win_count = (hctx->ccid3hctx_last_win_count +
@@ -1171,13 +1156,6 @@
hctx->ccid3hctx_rtt = (hctx->ccid3hctx_rtt * 9) / 10 +
r_sample / 10;
- /*
- * XXX: this is to avoid a division by zero in ccid3_hc_tx_packet_sent
- * implemention of the new window count.
- */
- if (hctx->ccid3hctx_rtt < 4)
- hctx->ccid3hctx_rtt = 4;
-
ccid3_pr_debug("%s, sk=%p, New RTT estimate=%uus, "
"r_sample=%us\n", dccp_role(sk), sk,
hctx->ccid3hctx_rtt, r_sample);
@@ -1220,21 +1198,14 @@
dccp_tx_hist_purge_older(ccid3_tx_hist,
&hctx->ccid3hctx_hist, packet);
- if (hctx->ccid3hctx_x < 10) {
- ccid3_pr_debug("ccid3_hc_tx_packet_recv hctx_x < 10\n");
- hctx->ccid3hctx_x = 10;
- }
- /* to prevent divide by zero below */
-
/*
* Schedule no feedback timer to expire in
* max(4 * R, 2 * s / X)
*/
next_tmout = max(hctx->ccid3hctx_t_rto,
- (2 * (hctx->ccid3hctx_s * 100000) /
- (hctx->ccid3hctx_x / 10)));
- /* maths with 100000 and 10 is to prevent overflow with 32 bit */
-
+ 2 * usecs_div(hctx->ccid3hctx_s,
+ hctx->ccid3hctx_x));
+
ccid3_pr_debug("%s, sk=%p, Scheduled no feedback timer to "
"expire in %lu jiffies (%luus)\n",
dccp_role(sk), sk,
@@ -1350,8 +1321,6 @@
/* Set transmission rate to 1 packet per second */
hctx->ccid3hctx_x = hctx->ccid3hctx_s;
- /* See ccid3_hc_tx_packet_sent win_count calculatation */
- hctx->ccid3hctx_rtt = 4;
hctx->ccid3hctx_t_rto = USEC_PER_SEC;
hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
INIT_LIST_HEAD(&hctx->ccid3hctx_hist);