[TCP]: Avoid two divides in __tcp_grow_window()

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bc2d5f7..519bd24 100644 (file)
--- 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)