* [PATCH net-next] tcp: remove loop to compute wscale
@ 2018-11-29 15:56 Eric Dumazet
2018-11-29 16:03 ` Soheil Hassas Yeganeh
2018-11-29 19:13 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Eric Dumazet @ 2018-11-29 15:56 UTC (permalink / raw)
To: David S . Miller
Cc: netdev, Eric Dumazet, Soheil Hassas Yeganeh, Neal Cardwell,
Yuchung Cheng, Eric Dumazet
We can remove the loop and conditional branches
and compute wscale efficiently thanks to ilog2()
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/ipv4/tcp_output.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3ae4a277991a3473f61b1f73acd5ee355cf6a5df..d3b691f3a9e896ce340ae081a0d24092024361c8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -233,16 +233,14 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
if (init_rcv_wnd)
*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
- (*rcv_wscale) = 0;
+ *rcv_wscale = 0;
if (wscale_ok) {
/* Set window scaling on max possible window */
space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
space = max_t(u32, space, sysctl_rmem_max);
space = min_t(u32, space, *window_clamp);
- while (space > U16_MAX && (*rcv_wscale) < TCP_MAX_WSCALE) {
- space >>= 1;
- (*rcv_wscale)++;
- }
+ *rcv_wscale = clamp_t(int, ilog2(space) - 15,
+ 0, TCP_MAX_WSCALE);
}
/* Set the clamp no higher than max representable value */
(*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
--
2.20.0.rc0.387.gc7a69e6b6c-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net-next] tcp: remove loop to compute wscale
2018-11-29 15:56 [PATCH net-next] tcp: remove loop to compute wscale Eric Dumazet
@ 2018-11-29 16:03 ` Soheil Hassas Yeganeh
2018-11-29 19:13 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Soheil Hassas Yeganeh @ 2018-11-29 16:03 UTC (permalink / raw)
To: Eric Dumazet
Cc: David Miller, netdev, Neal Cardwell, Yuchung Cheng, Eric Dumazet
On Thu, Nov 29, 2018 at 10:56 AM Eric Dumazet <edumazet@google.com> wrote:
>
> We can remove the loop and conditional branches
> and compute wscale efficiently thanks to ilog2()
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Very nice, thank you, Eric!
> ---
> net/ipv4/tcp_output.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 3ae4a277991a3473f61b1f73acd5ee355cf6a5df..d3b691f3a9e896ce340ae081a0d24092024361c8 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -233,16 +233,14 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
> if (init_rcv_wnd)
> *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
>
> - (*rcv_wscale) = 0;
> + *rcv_wscale = 0;
> if (wscale_ok) {
> /* Set window scaling on max possible window */
> space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
> space = max_t(u32, space, sysctl_rmem_max);
> space = min_t(u32, space, *window_clamp);
> - while (space > U16_MAX && (*rcv_wscale) < TCP_MAX_WSCALE) {
> - space >>= 1;
> - (*rcv_wscale)++;
> - }
> + *rcv_wscale = clamp_t(int, ilog2(space) - 15,
> + 0, TCP_MAX_WSCALE);
> }
> /* Set the clamp no higher than max representable value */
> (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
> --
> 2.20.0.rc0.387.gc7a69e6b6c-goog
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net-next] tcp: remove loop to compute wscale
2018-11-29 15:56 [PATCH net-next] tcp: remove loop to compute wscale Eric Dumazet
2018-11-29 16:03 ` Soheil Hassas Yeganeh
@ 2018-11-29 19:13 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2018-11-29 19:13 UTC (permalink / raw)
To: edumazet; +Cc: netdev, soheil, ncardwell, ycheng, eric.dumazet
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 29 Nov 2018 07:56:20 -0800
> We can remove the loop and conditional branches
> and compute wscale efficiently thanks to ilog2()
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
Applied.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-11-29 15:56 [PATCH net-next] tcp: remove loop to compute wscale Eric Dumazet
2018-11-29 16:03 ` Soheil Hassas Yeganeh
2018-11-29 19:13 ` David Miller
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