From: Eric Dumazet Date: Wed, 15 May 2013 19:25:55 +0000 (+0000) Subject: tcp: speedup tcp_fixup_rcvbuf() X-Git-Tag: next-20130521~54^2~41 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d2cf43674e17ca1c16c68d46d987d2f17bf7c371;p=karo-tx-linux.git tcp: speedup tcp_fixup_rcvbuf() tcp_fixup_rcvbuf() contains a loop to estimate initial socket rcv space needed for a given mss. With large MTU (like 64K on lo), we can loop ~500 times and consume a lot of cpu cycles. perf top of 200 concurrent netperf -t TCP_CRR 5.62% netperf [kernel.kallsyms] [k] tcp_init_buffer_space 1.71% netperf [kernel.kallsyms] [k] _raw_spin_lock 1.55% netperf [kernel.kallsyms] [k] kmem_cache_free 1.51% netperf [kernel.kallsyms] [k] tcp_transmit_skb 1.50% netperf [kernel.kallsyms] [k] tcp_ack Lets use a 100% factor, and remove the loop. 100% is needed anyway for tcp_adv_win_scale=1 default value, and is also the maximum factor. Refs: commit b49960a05e32 ("tcp: change tcp_adv_win_scale and tcp_rmem[2]") Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 08bbe6096528..b358e8c98607 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -360,9 +360,7 @@ static void tcp_fixup_rcvbuf(struct sock *sk) if (mss > 1460) icwnd = max_t(u32, (1460 * TCP_DEFAULT_INIT_RCVWND) / mss, 2); - rcvmem = SKB_TRUESIZE(mss + MAX_TCP_HEADER); - while (tcp_win_from_space(rcvmem) < mss) - rcvmem += 128; + rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER); rcvmem *= icwnd;