On 23/01/2017 15:34, Bruce Evans wrote: > 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.
Will do. > What is a good benchmark for showing that the fix helps? Honestly, I do not know. We ran into a pathology where a thread was not getting scheduled for a long time after being preempted while in a critical section (so the actual preemption was a voluntary switch when exiting the critical section). I am not sure what kind of a synthetic benchmark or a test case would readily demonstrate the problem. > 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. -- Andriy Gapon _______________________________________________ svn-src-stable-10@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-stable-10 To unsubscribe, send any mail to "svn-src-stable-10-unsubscr...@freebsd.org"
