lkml.org 
[lkml]   [2017]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH] tcp_nv: use do_div() instead of expensive div64_u64()
From
Date
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
\
 
 \ /
  Last update: 2017-11-02 15:07    [W:0.050 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site