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authorEric Dumazet <edumazet@google.com>2013-05-15 23:25:55 +0400
committerDavid S. Miller <davem@davemloft.net>2013-05-17 02:19:45 +0400
commitd2cf43674e17ca1c16c68d46d987d2f17bf7c371 (patch)
treef308a56b13f27297349f44f785f3c5d0d651ac07 /net/ipv4
parentdbbffe6898fd0d7bac66ded5d3c58835b13ddefc (diff)
downloadlinux-d2cf43674e17ca1c16c68d46d987d2f17bf7c371.tar.xz
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 <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp_input.c4
1 files changed, 1 insertions, 3 deletions
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;