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Message-Id: <20190528183425.31691-1-sergej.benilov@googlemail.com> Date: Tue, 28 May 2019 20:34:25 +0200 From: Sergej Benilov <sergej.benilov@...glemail.com> To: davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org Cc: Sergej Benilov <sergej.benilov@...glemail.com> Subject: [PATCH] v3.19.8: tcp: re-enable high throughput for low pacing rate Since commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 "tcp: refine TSO autosizing", the TSQ limit is computed as the smaller of sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10). For low pacing rates, this approach sets a low limit, reducing throughput dramatically. Compute the limit as the greater of sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10). Test: netperf -H remote -l -2000000 -- -s 1000000 before patch: MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 327680 327680 250.17 0.06 after patch: MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 327680 327680 1.29 12.54 Signed-off-by: Sergej Benilov <sergej.benilov@...glemail.com> --- net/ipv4/tcp_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index e625be56..71efca72 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2054,7 +2054,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, * One example is wifi aggregation (802.11 AMPDU) */ limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10); - limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes); + limit = max_t(u32, limit, sysctl_tcp_limit_output_bytes); if (atomic_read(&sk->sk_wmem_alloc) > limit) { set_bit(TSQ_THROTTLED, &tp->tsq_flags); -- 2.17.1
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