* [PATCH] tcp_nv: use do_div() instead of expensive div64_u64()
@ 2017-11-02 14:07 Konstantin Khlebnikov
2017-11-04 13:35 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Konstantin Khlebnikov @ 2017-11-02 14:07 UTC (permalink / raw)
To: netdev, David S. Miller
Cc: Stephen Hemminger, Lawrence Brakmo, linux-kernel, Eric Dumazet
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>
---
net/ipv4/tcp_nv.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
index 125fc1450b01..17e290ffcd80 100644
--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -209,7 +209,7 @@ 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;
@@ -251,8 +251,9 @@ 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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tcp_nv: use do_div() instead of expensive div64_u64()
2017-11-02 14:07 [PATCH] tcp_nv: use do_div() instead of expensive div64_u64() Konstantin Khlebnikov
@ 2017-11-04 13:35 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2017-11-04 13:35 UTC (permalink / raw)
To: khlebnikov; +Cc: netdev, stephen, brakmo, linux-kernel, eric.dumazet
From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Date: Thu, 02 Nov 2017 17:07:05 +0300
> 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>
Applied to net-next, thank you.
^ permalink raw reply [flat|nested] 2+ messages in thread
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