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linux config: Set TCP_CONG_CUBIC=yes to restore the default

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This will switch the default TCP congestion control algorithm from
new Reno to CUBIC. CUBIC is the default since Linux kernel 2.6.19
(see 597811ec167fa) and most (all?) distributions keep this default
(e.g. Debian and Ubuntu). On NixOS the default was still new Reno
because generate-config.pl changes TCP_CONG_CUBIC from y to m (since we
try to build everything as a module by default).

To check the active and available algorithms:
$ sysctl net.ipv4.tcp_congestion_control
net.ipv4.tcp_congestion_control = cubic
$ sysctl net.ipv4.tcp_available_congestion_control
net.ipv4.tcp_available_congestion_control = cubic reno

Note: E.g. x86_64_defconfig sets TCP_CONG_CUBIC=y indirectly via
CONFIG_TCP_CONG_ADVANCED=y (but CUBIC is also the default if set to no,
see net/ipv4/Kconfig).
This commit is contained in:
Michael Weiss 2020-02-23 18:45:29 +01:00
parent c3c47544e0
commit 60f4345e37
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pkgs/os-specific/linux/kernel/common-config.nix
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@ -120,6 +120,7 @@ let
XDP_SOCKETS = whenAtLeast "4.19" yes;
XDP_SOCKETS_DIAG = whenAtLeast "4.19" yes;
WAN = yes;
TCP_CONG_CUBIC = yes; # This is the default congestion control algorithm since 2.6.19
# Required by systemd per-cgroup firewalling
CGROUP_BPF = option yes;
CGROUP_NET_PRIO = yes; # Required by systemd