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Diffstat (limited to 'net/ipv4/tcp_vegas.c')
-rw-r--r--net/ipv4/tcp_vegas.c113
1 files changed, 32 insertions, 81 deletions
diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index be24d6ee34b..9a5e05f27f4 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -40,18 +40,14 @@
#include "tcp_vegas.h"
-/* Default values of the Vegas variables, in fixed-point representation
- * with V_PARAM_SHIFT bits to the right of the binary point.
- */
-#define V_PARAM_SHIFT 1
-static int alpha = 2<<V_PARAM_SHIFT;
-static int beta = 4<<V_PARAM_SHIFT;
-static int gamma = 1<<V_PARAM_SHIFT;
+static int alpha = 2;
+static int beta = 4;
+static int gamma = 1;
module_param(alpha, int, 0644);
-MODULE_PARM_DESC(alpha, "lower bound of packets in network (scale by 2)");
+MODULE_PARM_DESC(alpha, "lower bound of packets in network");
module_param(beta, int, 0644);
-MODULE_PARM_DESC(beta, "upper bound of packets in network (scale by 2)");
+MODULE_PARM_DESC(beta, "upper bound of packets in network");
module_param(gamma, int, 0644);
MODULE_PARM_DESC(gamma, "limit on increase (scale by 2)");
@@ -162,57 +158,28 @@ void tcp_vegas_cwnd_event(struct sock *sk, enum tcp_ca_event event)
}
EXPORT_SYMBOL_GPL(tcp_vegas_cwnd_event);
-static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
+static inline u32 tcp_vegas_ssthresh(struct tcp_sock *tp)
+{
+ return min(tp->snd_ssthresh, tp->snd_cwnd-1);
+}
+
+static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
struct tcp_sock *tp = tcp_sk(sk);
struct vegas *vegas = inet_csk_ca(sk);
- if (!vegas->doing_vegas_now)
- return tcp_reno_cong_avoid(sk, ack, in_flight);
-
- /* The key players are v_beg_snd_una and v_beg_snd_nxt.
- *
- * These are so named because they represent the approximate values
- * of snd_una and snd_nxt at the beginning of the current RTT. More
- * precisely, they represent the amount of data sent during the RTT.
- * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
- * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
- * bytes of data have been ACKed during the course of the RTT, giving
- * an "actual" rate of:
- *
- * (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
- *
- * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
- * because delayed ACKs can cover more than one segment, so they
- * don't line up nicely with the boundaries of RTTs.
- *
- * Another unfortunate fact of life is that delayed ACKs delay the
- * advance of the left edge of our send window, so that the number
- * of bytes we send in an RTT is often less than our cwnd will allow.
- * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
- */
+ if (!vegas->doing_vegas_now) {
+ tcp_reno_cong_avoid(sk, ack, acked);
+ return;
+ }
if (after(ack, vegas->beg_snd_nxt)) {
/* Do the Vegas once-per-RTT cwnd adjustment. */
- u32 old_wnd, old_snd_cwnd;
-
-
- /* Here old_wnd is essentially the window of data that was
- * sent during the previous RTT, and has all
- * been acknowledged in the course of the RTT that ended
- * with the ACK we just received. Likewise, old_snd_cwnd
- * is the cwnd during the previous RTT.
- */
- old_wnd = (vegas->beg_snd_nxt - vegas->beg_snd_una) /
- tp->mss_cache;
- old_snd_cwnd = vegas->beg_snd_cwnd;
/* Save the extent of the current window so we can use this
* at the end of the next RTT.
*/
- vegas->beg_snd_una = vegas->beg_snd_nxt;
vegas->beg_snd_nxt = tp->snd_nxt;
- vegas->beg_snd_cwnd = tp->snd_cwnd;
/* We do the Vegas calculations only if we got enough RTT
* samples that we can be reasonably sure that we got
@@ -227,9 +194,10 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
/* We don't have enough RTT samples to do the Vegas
* calculation, so we'll behave like Reno.
*/
- tcp_reno_cong_avoid(sk, ack, in_flight);
+ tcp_reno_cong_avoid(sk, ack, acked);
} else {
- u32 rtt, target_cwnd, diff;
+ u32 rtt, diff;
+ u64 target_cwnd;
/* We have enough RTT samples, so, using the Vegas
* algorithm, we determine if we should increase or
@@ -249,27 +217,19 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
*
* This is:
* (actual rate in segments) * baseRTT
- * We keep it as a fixed point number with
- * V_PARAM_SHIFT bits to the right of the binary point.
*/
- target_cwnd = ((old_wnd * vegas->baseRTT)
- << V_PARAM_SHIFT) / rtt;
+ target_cwnd = tp->snd_cwnd * vegas->baseRTT / rtt;
/* Calculate the difference between the window we had,
* and the window we would like to have. This quantity
* is the "Diff" from the Arizona Vegas papers.
- *
- * Again, this is a fixed point number with
- * V_PARAM_SHIFT bits to the right of the binary
- * point.
*/
- diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
+ diff = tp->snd_cwnd * (rtt-vegas->baseRTT) / vegas->baseRTT;
- if (diff > gamma && tp->snd_ssthresh > 2 ) {
+ if (diff > gamma && tp->snd_cwnd <= tp->snd_ssthresh) {
/* Going too fast. Time to slow down
* and switch to congestion avoidance.
*/
- tp->snd_ssthresh = 2;
/* Set cwnd to match the actual rate
* exactly:
@@ -278,16 +238,14 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
* truncation robs us of full link
* utilization.
*/
- tp->snd_cwnd = min(tp->snd_cwnd,
- (target_cwnd >>
- V_PARAM_SHIFT)+1);
+ tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);
+ tp->snd_ssthresh = tcp_vegas_ssthresh(tp);
} else if (tp->snd_cwnd <= tp->snd_ssthresh) {
/* Slow start. */
- tcp_slow_start(tp);
+ tcp_slow_start(tp, acked);
} else {
/* Congestion avoidance. */
- u32 next_snd_cwnd;
/* Figure out where we would like cwnd
* to be.
@@ -296,32 +254,27 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
/* The old window was too fast, so
* we slow down.
*/
- next_snd_cwnd = old_snd_cwnd - 1;
+ tp->snd_cwnd--;
+ tp->snd_ssthresh
+ = tcp_vegas_ssthresh(tp);
} else if (diff < alpha) {
/* We don't have enough extra packets
* in the network, so speed up.
*/
- next_snd_cwnd = old_snd_cwnd + 1;
+ tp->snd_cwnd++;
} else {
/* Sending just as fast as we
* should be.
*/
- next_snd_cwnd = old_snd_cwnd;
}
-
- /* Adjust cwnd upward or downward, toward the
- * desired value.
- */
- if (next_snd_cwnd > tp->snd_cwnd)
- tp->snd_cwnd++;
- else if (next_snd_cwnd < tp->snd_cwnd)
- tp->snd_cwnd--;
}
if (tp->snd_cwnd < 2)
tp->snd_cwnd = 2;
else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
tp->snd_cwnd = tp->snd_cwnd_clamp;
+
+ tp->snd_ssthresh = tcp_current_ssthresh(sk);
}
/* Wipe the slate clean for the next RTT. */
@@ -330,7 +283,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
}
/* Use normal slow start */
else if (tp->snd_cwnd <= tp->snd_ssthresh)
- tcp_slow_start(tp);
+ tcp_slow_start(tp, acked);
}
@@ -351,12 +304,10 @@ void tcp_vegas_get_info(struct sock *sk, u32 ext, struct sk_buff *skb)
}
EXPORT_SYMBOL_GPL(tcp_vegas_get_info);
-static struct tcp_congestion_ops tcp_vegas = {
- .flags = TCP_CONG_RTT_STAMP,
+static struct tcp_congestion_ops tcp_vegas __read_mostly = {
.init = tcp_vegas_init,
.ssthresh = tcp_reno_ssthresh,
.cong_avoid = tcp_vegas_cong_avoid,
- .min_cwnd = tcp_reno_min_cwnd,
.pkts_acked = tcp_vegas_pkts_acked,
.set_state = tcp_vegas_state,
.cwnd_event = tcp_vegas_cwnd_event,
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-10 06:13:42 +0000