From 43e122b014c955a33220fabbd09c4b5e4f422c3c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 21 Aug 2015 17:38:02 -0700 Subject: tcp: refine pacing rate determination When TCP pacing was added back in linux-3.12, we chose to apply a fixed ratio of 200 % against current rate, to allow probing for optimal throughput even during slow start phase, where cwnd can be doubled every other gRTT. At Google, we found it was better applying a different ratio while in Congestion Avoidance phase. This ratio was set to 120 %. We've used the normal tcp_in_slow_start() helper for a while, then tuned the condition to select the conservative ratio as soon as cwnd >= ssthresh/2 : - After cwnd reduction, it is safer to ramp up more slowly, as we approach optimal cwnd. - Initial ramp up (ssthresh == INFINITY) still allows doubling cwnd every other RTT. Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- include/net/tcp.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/net/tcp.h') diff --git a/include/net/tcp.h b/include/net/tcp.h index 309801f7eb82..4a7b03947a38 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -281,6 +281,8 @@ extern unsigned int sysctl_tcp_notsent_lowat; extern int sysctl_tcp_min_tso_segs; extern int sysctl_tcp_autocorking; extern int sysctl_tcp_invalid_ratelimit; +extern int sysctl_tcp_pacing_ss_ratio; +extern int sysctl_tcp_pacing_ca_ratio; extern atomic_long_t tcp_memory_allocated; extern struct percpu_counter tcp_sockets_allocated; -- cgit v1.2.3