svn commit: r307319 - in head/sys/netinet: . tcp_stacks

[Slawa Olhovchenkov]

On Fri, Oct 14, 2016 at 02:57:43PM +0000, Jonathan T. Looney wrote:

> Author: jtl
> Date: Fri Oct 14 14:57:43 2016
> New Revision: 307319
> URL: https://svnweb.freebsd.org/changeset/base/307319
> 
> Log:
>   The code currently resets the keepalive timer each time a packet is
>   received on a TCP session that has entered the ESTABLISHED state. This
>   results in a lot of calls to reset the keepalive timer.
>   
>   This patch changes the behavior so we set the keepalive timer for the
>   keepalive idle time (TP_KEEPIDLE). When the keepalive timer fires, it will
>   first check to see if the session has been idle for TP_KEEPIDLE ticks. If
>   not, it will reschedule the keepalive timer for the time the session will
>   have been idle for TP_KEEPIDLE ticks.
>   
>   For a session with regular communication, the keepalive timer should fire
>   approximately once every TP_KEEPIDLE ticks. For sessions with irregular
>   communication, the keepalive timer might fire more often. But, the
>   disruption from a periodic keepalive timer should be less than the regular
>   cost of resetting the keepalive timer on every packet.
>   
>   (FWIW, this change saved approximately 1.73% of the busy CPU cycles on a
>   particular test system with a heavy TCP output load. Of course, the
>   actual impact is very specific to the particular hardware and workload.)
>   
>   Reviewed by:	gallatin, rrs
>   MFC after:	2 weeks
>   Sponsored by:	Netflix
>   Differential Revision:	https://reviews.freebsd.org/D8243

Some issus exist?