1 files changed, 5 insertions, 59 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index dad3e7eeed94..6886f386464f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2879,67 +2879,13 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
         *rexmit = REXMIT_LOST;
 }
 
-/* Kathleen Nichols' algorithm for tracking the minimum value of
- * a data stream over some fixed time interval. (E.g., the minimum
- * RTT over the past five minutes.) It uses constant space and constant
- * time per update yet almost always delivers the same minimum as an
- * implementation that has to keep all the data in the window.
- *
- * The algorithm keeps track of the best, 2nd best & 3rd best min
- * values, maintaining an invariant that the measurement time of the
- * n'th best >= n-1'th best. It also makes sure that the three values
- * are widely separated in the time window since that bounds the worse
- * case error when that data is monotonically increasing over the window.
- *
- * Upon getting a new min, we can forget everything earlier because it
- * has no value - the new min is <= everything else in the window by
- * definition and it's the most recent. So we restart fresh on every new min
- * and overwrites 2nd & 3rd choices. The same property holds for 2nd & 3rd
- * best.
- */
 static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us)
 {
-        const u32 now = tcp_time_stamp, wlen = sysctl_tcp_min_rtt_wlen * HZ;
-        struct rtt_meas *m = tcp_sk(sk)->rtt_min;
-        struct rtt_meas rttm = {
-                .rtt = likely(rtt_us) ? rtt_us : jiffies_to_usecs(1),
-                .ts = now,
-        };
-        u32 elapsed;
-
-        /* Check if the new measurement updates the 1st, 2nd, or 3rd choices */
-        if (unlikely(rttm.rtt <= m[0].rtt))
-                m[0] = m[1] = m[2] = rttm;
-        else if (rttm.rtt <= m[1].rtt)
-                m[1] = m[2] = rttm;
-        else if (rttm.rtt <= m[2].rtt)
-                m[2] = rttm;
-
-        elapsed = now - m[0].ts;
-        if (unlikely(elapsed > wlen)) {
-                /* Passed entire window without a new min so make 2nd choice
-                 * the new min & 3rd choice the new 2nd. So forth and so on.
-                 */
-                m[0] = m[1];
-                m[1] = m[2];
-                m[2] = rttm;
-                if (now - m[0].ts > wlen) {
-                        m[0] = m[1];
-                        m[1] = rttm;
-                        if (now - m[0].ts > wlen)
-                                m[0] = rttm;
-                }
-        } else if (m[1].ts == m[0].ts && elapsed > wlen / 4) {
-                /* Passed a quarter of the window without a new min so
-                 * take 2nd choice from the 2nd quarter of the window.
-                 */
-                m[2] = m[1] = rttm;
-        } else if (m[2].ts == m[1].ts && elapsed > wlen / 2) {
-                /* Passed half the window without a new min so take the 3rd
-                 * choice from the last half of the window.
-                 */
-                m[2] = rttm;
-        }
+        struct tcp_sock *tp = tcp_sk(sk);
+        u32 wlen = sysctl_tcp_min_rtt_wlen * HZ;
+
+        minmax_running_min(&tp->rtt_min, wlen, tcp_time_stamp,
+                           rtt_us ? : jiffies_to_usecs(1));
 }
 
 static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,