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author | Eric Dumazet <edumazet@google.com> | 2015-08-22 02:38:02 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2015-08-25 20:33:54 +0200 |
commit | 43e122b014c955a33220fabbd09c4b5e4f422c3c (patch) | |
tree | a5accf2276666812aed04749e3b6f44505a5cbab /include/net/tcp.h | |
parent | xfrm: Use VRF master index if output device is enslaved (diff) | |
download | linux-43e122b014c955a33220fabbd09c4b5e4f422c3c.tar.xz linux-43e122b014c955a33220fabbd09c4b5e4f422c3c.zip |
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/net/tcp.h')
-rw-r--r-- | include/net/tcp.h | 2 |
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; |