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authorEric Dumazet <edumazet@google.com>2015-08-22 03:38:02 +0300
committerDavid S. Miller <davem@davemloft.net>2015-08-25 21:33:54 +0300
commit43e122b014c955a33220fabbd09c4b5e4f422c3c (patch)
treea5accf2276666812aed04749e3b6f44505a5cbab /include
parent4ec3b28c2763e11a423d03810ff0be65f02e635e (diff)
downloadlinux-43e122b014c955a33220fabbd09c4b5e4f422c3c.tar.xz
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 <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 'include')
-rw-r--r--include/net/tcp.h2
1 files changed, 2 insertions, 0 deletions
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;