svn commit: r312666 - stable/10/sys/kern

[Bruce Evans]

On Mon, 23 Jan 2017, Andriy Gapon wrote:

> ==============================================================================
> --- stable/10/sys/kern/sched_4bsd.c	Mon Jan 23 08:34:41 2017	(r312665)
> +++ stable/10/sys/kern/sched_4bsd.c	Mon Jan 23 08:34:51 2017	(r312666)
> @@ -963,8 +963,8 @@ sched_switch(struct thread *td, struct t
> 		sched_load_rem();
>
> 	td->td_lastcpu = td->td_oncpu;
> -	preempted = !((td->td_flags & TDF_SLICEEND) ||
> -	    (flags & SWT_RELINQUISH));
> +	preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
> +	    (flags & SW_PREEMPT) != 0;
> 	td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
> 	td->td_owepreempt = 0;
> 	td->td_oncpu = NOCPU;

Please also merge to FreeBSD-9.  FreeBSD-9 has best performance for a
makeworld benchmark.

What is a good benchmark for showing that the fix helps?

Involuntary context switches increased by almost a factor of 2 for the
makeworld benchmark (over nfs) recently, but that was just caused by
pessimizations in the NIC driver.

Bruce