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Date: Thu, 3 Oct 2013 09:56:43 +0200
From: Daniel Borkmann <dborkman@...hat.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
Francesco Fusco <ffusco@...hat.com>
Subject: [PATCH net-next] tcp: rcvbuf autotuning improvements
This is a complementary patch for commit 6ae705323 ("tcp: sndbuf
autotuning improvements") that fixes a performance regression on
receiver side in setups with low to mid latency, high throughput,
and senders with TSO/GSO off (receivers w/ default settings).
The following measurements in Mbit/s were done for 60sec w/ netperf
on virtio w/ TSO/GSO off:
(ms) 1) 2) 3)
0 2762.11 1150.32 2906.17
10 1083.61 538.89 1091.03
25 471.81 313.18 474.60
50 242.33 187.84 242.36
75 162.14 134.45 161.95
100 121.55 101.96 121.49
150 80.64 57.75 80.48
200 58.97 54.11 59.90
250 47.10 46.92 47.31
Same setup w/ TSO/GSO on:
(ms) 1) 2) 3)
0 12225.91 12366.89 16514.37
10 1526.64 1525.79 2176.63
25 655.13 647.79 871.52
50 338.51 377.88 439.46
75 246.49 278.46 295.62
100 210.93 207.56 217.34
150 127.88 129.56 141.33
200 94.95 94.50 107.29
250 67.39 73.88 88.35
Similarly as in 6ae705323, we fixed up power-of-two rounding and
took cached mss into account, thus bringing per_mss calculations
closer to each other, the rest stays as is.
We also renamed tcp_fixup_rcvbuf() to tcp_rcvbuf_expand() to be
consistent with tcp_sndbuf_expand().
While we do think that 6ae705323b71 is the right way to go, also
this follow-up seems necessary to restore performance for
receivers.
For the evaluation, same kernels on each host were used:
1) net-next (4fbef95af), which is before 6ae705323
2) net-next (6ae705323), which is sndbuf improvements
3) net-next (6ae705323), plus this patch on top
This was done in joint work with Francesco Fusco.
Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
Signed-off-by: Francesco Fusco <ffusco@...hat.com>
---
net/ipv4/tcp_input.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cd65674..ed37b1d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -367,13 +367,19 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
}
/* 3. Tuning rcvbuf, when connection enters established state. */
-static void tcp_fixup_rcvbuf(struct sock *sk)
+static void tcp_rcvbuf_expand(struct sock *sk)
{
- u32 mss = tcp_sk(sk)->advmss;
- int rcvmem;
+ const struct tcp_sock *tp = tcp_sk(sk);
+ int rcvmem, per_mss;
+
+ per_mss = max_t(u32, tp->advmss, tp->mss_cache) +
+ MAX_TCP_HEADER +
+ SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+
+ per_mss = roundup_pow_of_two(per_mss) +
+ SKB_DATA_ALIGN(sizeof(struct sk_buff));
- rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
- tcp_default_init_rwnd(mss);
+ rcvmem = 2 * tcp_default_init_rwnd(per_mss) * per_mss;
/* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
* Allow enough cushion so that sender is not limited by our window
@@ -394,7 +400,7 @@ void tcp_init_buffer_space(struct sock *sk)
int maxwin;
if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
- tcp_fixup_rcvbuf(sk);
+ tcp_rcvbuf_expand(sk);
if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
tcp_sndbuf_expand(sk);
--
1.7.11.7
--
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