[PATCH 5/7] tcp_cubic: enable high resolution ack time if needed
From: Stephen Hemminger <hidden>
Date: 2011-03-14 18:02:04
This is a refined version of an earlier patch by Lucas Nussbaum. Cubic needs RTT values in milliseconds. If HZ < 1000 then the values will be too coarse. Signed-off-by: Stephen Hemminger <redacted> Reported-by: Lucas Nussbaum <redacted>
--- a/net/ipv4/tcp_cubic.c 2011-03-14 08:22:42.486690594 -0700
+++ b/net/ipv4/tcp_cubic.c 2011-03-14 08:27:24.435852847 -0700@@ -459,6 +459,10 @@ static int __init cubictcp_register(void /* divide by bic_scale and by constant Srtt (100ms) */ do_div(cube_factor, bic_scale * 10); + /* hystart needs ms clock resolution */ + if (hystart && HZ < 1000) + cubictcp.flags |= TCP_CONG_RTT_STAMP; + return tcp_register_congestion_control(&cubictcp); }