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| author |   Kevin(Yudong) Yang <yyd@google.com> | 2019-12-09 14:19:59 -0500 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2019-12-09 20:17:48 -0800 |
| commit | 65e6d90168f3593df0ae598502bcbf20d78ff0fb (patch) | |
| tree | f8a7670488d31167eb0fdce6033859caee7de056 /Documentation | |
| parent | sctp: get netns from asoc and ep base (diff) | |
| download | linux-dev-65e6d90168f3593df0ae598502bcbf20d78ff0fb.tar.xz linux-dev-65e6d90168f3593df0ae598502bcbf20d78ff0fb.zip | |
net-tcp: Disable TCP ssthresh metrics cache by default
This patch introduces a sysctl knob "net.ipv4.tcp_no_ssthresh_metrics_save"
that disables TCP ssthresh metrics cache by default. Other parts of TCP
metrics cache, e.g. rtt, cwnd, remain unchanged.
As modern networks becoming more and more dynamic, TCP metrics cache
today often causes more harm than benefits. For example, the same IP
address is often shared by different subscribers behind NAT in residential
networks. Even if the IP address is not shared by different users,
caching the slow-start threshold of a previous short flow using loss-based
congestion control (e.g. cubic) often causes the future longer flows of
the same network path to exit slow-start prematurely with abysmal
throughput.
Caching ssthresh is very risky and can lead to terrible performance.
Therefore it makes sense to make disabling ssthresh caching by
default and opt-in for specific networks by the administrators.
This practice also has worked well for several years of deployment with
CUBIC congestion control at Google.
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Kevin(Yudong) Yang <yyd@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index fd26788e8c96..90b8f14bc41a 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -479,6 +479,10 @@ tcp_no_metrics_save - BOOLEAN degradation. If set, TCP will not cache metrics on closing connections. +tcp_no_ssthresh_metrics_save - BOOLEAN + Controls whether TCP saves ssthresh metrics in the route cache. + Default is 1, which disables ssthresh metrics. + tcp_orphan_retries - INTEGER This value influences the timeout of a locally closed TCP connection, when RTO retransmissions remain unacknowledged. |