1 files changed, 12 insertions, 70 deletions

diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 14504dada116..a453aac91bd3 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)");
 
@@ -172,49 +168,13 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
                 return;
         }
 
-        /* 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 (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
@@ -252,22 +212,14 @@ 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 = ((u64)old_wnd * vegas->baseRTT);
-                        target_cwnd <<= V_PARAM_SHIFT;
-                        do_div(target_cwnd, 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 ) {
                                 /* Going too fast. Time to slow down
@@ -282,16 +234,13 @@ 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,
-                                                   ((u32)target_cwnd >>
-                                                    V_PARAM_SHIFT)+1);
+                                tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);
 
                         } else if (tp->snd_cwnd <= tp->snd_ssthresh) {
                                 /* Slow start.  */
                                 tcp_slow_start(tp);
                         } else {
                                 /* Congestion avoidance. */
-                                u32 next_snd_cwnd;
 
                                 /* Figure out where we would like cwnd
                                  * to be.
@@ -300,32 +249,25 @@ 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--;
                                 } 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. */