* [TCP] Avoid two divides in __tcp_grow_window()
@ 2007-12-21 14:05 Eric Dumazet
2007-12-21 14:08 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Eric Dumazet @ 2007-12-21 14:05 UTC (permalink / raw)
To: David Miller; +Cc: netdev@vger.kernel.org
tcp_win_from_space() being signed, compiler might emit an integer divide
to compute tcp_win_from_space()/2 .
Using right shifts is OK here and less expensive.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6931946..145b51a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -289,8 +289,8 @@ static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
{
struct tcp_sock *tp = tcp_sk(sk);
/* Optimize this! */
- int truesize = tcp_win_from_space(skb->truesize)/2;
- int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
+ int truesize = tcp_win_from_space(skb->truesize) >> 1;
+ int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
while (tp->rcv_ssthresh <= window) {
if (truesize <= skb->len)
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [TCP] Avoid two divides in __tcp_grow_window()
2007-12-21 14:05 [TCP] Avoid two divides in __tcp_grow_window() Eric Dumazet
@ 2007-12-21 14:08 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2007-12-21 14:08 UTC (permalink / raw)
To: dada1; +Cc: netdev
From: Eric Dumazet <dada1@cosmosbay.com>
Date: Fri, 21 Dec 2007 15:05:51 +0100
> tcp_win_from_space() being signed, compiler might emit an integer divide
> to compute tcp_win_from_space()/2 .
>
> Using right shifts is OK here and less expensive.
>
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Applied, thanks Eric.
^ permalink raw reply [flat|nested] 2+ messages in thread
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