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| author | Eric Dumazet <edumazet@google.com> | 2015-08-21 17:38:02 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-08-25 11:33:54 -0700 |
| commit | 43e122b014c955a33220fabbd09c4b5e4f422c3c (patch) | |
| tree | a5accf2276666812aed04749e3b6f44505a5cbab /net/ipv4/sysctl_net_ipv4.c | |
| parent | 4ec3b28c2763e11a423d03810ff0be65f02e635e (diff) | |
| download | linux-43e122b014c955a33220fabbd09c4b5e4f422c3c.tar.gz linux-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 'net/ipv4/sysctl_net_ipv4.c')
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 0330ab2e2b63..879bdc5c95b1 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -29,6 +29,7 @@ static int zero; static int one = 1; static int four = 4; +static int thousand = 1000; static int gso_max_segs = GSO_MAX_SEGS; static int tcp_retr1_max = 255; static int ip_local_port_range_min[] = { 1, 1 }; @@ -712,6 +713,24 @@ static struct ctl_table ipv4_table[] = { .extra2 = &gso_max_segs, }, { + .procname = "tcp_pacing_ss_ratio", + .data = &sysctl_tcp_pacing_ss_ratio, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &thousand, + }, + { + .procname = "tcp_pacing_ca_ratio", + .data = &sysctl_tcp_pacing_ca_ratio, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &thousand, + }, + { .procname = "tcp_autocorking", .data = &sysctl_tcp_autocorking, .maxlen = sizeof(int), |