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| author | Maciej Żenczykowski <maze@google.com> | 2018-06-03 10:41:17 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-06-04 17:13:35 -0400 |
| commit | 79e9fed460385a3d8ba0b5782e9e74405cb199b1 (patch) | |
| tree | ed08428854481e17c476dcaf2f2ab8ddf5038d45 /Documentation/networking | |
| parent | 39dbc646fd2c67ee9b71450ce172cbd714d4e7fb (diff) | |
| download | linux-79e9fed460385a3d8ba0b5782e9e74405cb199b1.tar.bz2 | |
net-tcp: extend tcp_tw_reuse sysctl to enable loopback only optimization
This changes the /proc/sys/net/ipv4/tcp_tw_reuse from a boolean
to an integer.
It now takes the values 0, 1 and 2, where 0 and 1 behave as before,
while 2 enables timewait socket reuse only for sockets that we can
prove are loopback connections:
ie. bound to 'lo' interface or where one of source or destination
IPs is 127.0.0.0/8, ::ffff:127.0.0.0/104 or ::1.
This enables quicker reuse of ephemeral ports for loopback connections
- where tcp_tw_reuse is 100% safe from a protocol perspective
(this assumes no artificially induced packet loss on 'lo').
This also makes estblishing many loopback connections *much* faster
(allocating ports out of the first half of the ephemeral port range
is significantly faster, then allocating from the second half)
Without this change in a 32K ephemeral port space my sample program
(it just establishes and closes [::1]:ephemeral -> [::1]:server_port
connections in a tight loop) fails after 32765 connections in 24 seconds.
With it enabled 50000 connections only take 4.7 seconds.
This is particularly problematic for IPv6 where we only have one local
address and cannot play tricks with varying source IP from 127.0.0.0/8
pool.
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Wei Wang <weiwan@google.com>
Change-Id: I0377961749979d0301b7b62871a32a4b34b654e1
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 924bd51327b7..6841c74eac00 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -667,11 +667,15 @@ tcp_tso_win_divisor - INTEGER building larger TSO frames. Default: 3 -tcp_tw_reuse - BOOLEAN - Allow to reuse TIME-WAIT sockets for new connections when it is - safe from protocol viewpoint. Default value is 0. +tcp_tw_reuse - INTEGER + Enable reuse of TIME-WAIT sockets for new connections when it is + safe from protocol viewpoint. + 0 - disable + 1 - global enable + 2 - enable for loopback traffic only It should not be changed without advice/request of technical experts. + Default: 2 tcp_window_scaling - BOOLEAN Enable window scaling as defined in RFC1323. |