On Tue, 28 Mar 2017 17:01:52 -0400 Rik van Riel <r...@redhat.com> wrote:
> On Tue, 2017-03-28 at 16:14 -0400, Luiz Capitulino wrote: > > On Tue, 28 Mar 2017 13:24:06 -0400 > > Luiz Capitulino <lcapitul...@redhat.com> wrote: > > > I'm starting to suspect that the nohz code may be programming > > > the tick period to be shorter than 1ms when it re-activates > > > the tick. > > > > And I think I was right, it looks like the nohz code is programming > > the tick period incorrectly when restarting the tick. The patch below > > fixes things for me, but I still have some homework todo and more > > testing before posting a patch for inclusion. Could you guys test it? > > Your patch seems to work. I don't claim to understand why > your patch makes a difference, but for this particular test > case, on this particular setup, it seems to work... I don't fully understand why either yet. I was looking for places where nohz might be programming the tick period incorrectly and I found that there's a case in tick_nohz_stop_sched_tick() where tick_nohz_restart() is called only to reprogram the tick timer, not cancel the tick. In this case, ts->last_tick seems to be out of date. Fixing this fixed accounting for me. > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > > index 7fe53be..9abe979 100644 > > --- a/kernel/time/tick-sched.c > > +++ b/kernel/time/tick-sched.c > > @@ -1152,6 +1152,7 @@ static enum hrtimer_restart > > tick_sched_timer(struct hrtimer *timer) > > struct pt_regs *regs = get_irq_regs(); > > ktime_t now = ktime_get(); > > > > + ts->last_tick = now; > > tick_sched_do_timer(now); > > > > /* >
