* [TCP] Avoid two divides in tcp_output.c
@ 2007-12-21 5:34 Eric Dumazet
2007-12-21 5:40 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Eric Dumazet @ 2007-12-21 5:34 UTC (permalink / raw)
To: David S. Miller; +Cc: Linux Netdev List
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Because 'free_space' variable in __tcp_select_window() is signed,
expression (free_space / 2) forces compiler to emit an integer divide.
This can be changed to a plain right shift, less expensive.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
[-- Attachment #2: tcp_output.patch --]
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diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7c50271..9a9510a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1627,7 +1627,7 @@ u32 __tcp_select_window(struct sock *sk)
if (mss > full_space)
mss = full_space;
- if (free_space < full_space/2) {
+ if (free_space < (full_space >> 1)) {
icsk->icsk_ack.quick = 0;
if (tcp_memory_pressure)
@@ -1666,7 +1666,7 @@ u32 __tcp_select_window(struct sock *sk)
if (window <= free_space - mss || window > free_space)
window = (free_space/mss)*mss;
else if (mss == full_space &&
- free_space > window + full_space/2)
+ free_space > window + (full_space >> 1))
window = free_space;
}
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [TCP] Avoid two divides in tcp_output.c
2007-12-21 5:34 [TCP] Avoid two divides in tcp_output.c Eric Dumazet
@ 2007-12-21 5:40 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2007-12-21 5:40 UTC (permalink / raw)
To: dada1; +Cc: netdev
From: Eric Dumazet <dada1@cosmosbay.com>
Date: Fri, 21 Dec 2007 06:34:28 +0100
> Because 'free_space' variable in __tcp_select_window() is signed,
> expression (free_space / 2) forces compiler to emit an integer divide.
>
> This can be changed to a plain right shift, less expensive.
>
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Applied to net-2.6.25, thanks Eric.
^ permalink raw reply [flat|nested] 2+ messages in thread
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