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tcp: remove loop to compute wscale 

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-11-29 07:56:20 -08:00 committed by David S. Miller
parent dcc6abae0f
commit 19bf62613a
1 changed files with 3 additions and 5 deletions
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8
net/ipv4/tcp_output.c
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@ -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);