tcp_nv: use do_div() instead of expensive div64_u64()

Average RTT is 32-bit thus full 64-bit division is redundant.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
index 0529e29..0b5a05b 100644 (file)
--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -242,7 +242,7 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample)
        struct tcp_sock *tp = tcp_sk(sk);
        struct tcpnv *ca = inet_csk_ca(sk);
        unsigned long now = jiffies;
-       s64 rate64 = 0;
+       u64 rate64;
        u32 rate, max_win, cwnd_by_slope;
        u32 avg_rtt;
        u32 bytes_acked = 0;
@@ -284,8 +284,9 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample)
        }
 
        /* rate in 100's bits per second */
-       rate64 = ((u64)sample->in_flight) * 8000000;
-       rate = (u32)div64_u64(rate64, (u64)(avg_rtt ?: 1) * 100);
+       rate64 = ((u64)sample->in_flight) * 80000;
+       do_div(rate64, avg_rtt ?: 1);
+       rate = (u32)rate64;
 
        /* Remember the maximum rate seen during this RTT
         * Note: It may be more than one RTT. This function should be