file: /proc/sys/net/ipv4/tcp_no_metrics_save
variable: net.ipv4.tcp_no_metrics_save
Official reference

By default, TCP saves various connection metrics in the route cache when the connection closes, so that connections established in the near future can use these to set initial conditions. Usually, this increases overall performance, but may sometimes cause performance degradation. If set, TCP will not cache metrics on closing connections.