On Tue, 2012-10-30 at 16:32 +0800, Charles Wang wrote:
> calc_load_exit_idle depends on updated jiffies, so you shouldn't move
> this before tick_do_update_jiffies64.
OK, so it should be moved to the end of the if block. Note, that was a
change I made, as that function was added since Frederic did his code. I
looked into the code and it seemed that it should be moved for just idle
as well. But I agree with you that it should be after the jiffies
update.
> And why should we do nohz_balance_enter_idle in tick_nohz_idle_exit?
> It's nohz_balance_exit_idle here.
OK, that's my fault as well. As Frederic's original patch just moved
select_nohz_load_balance(0). But the commit c1cc017c59 "sched/nohz:
Clean up select_nohz_load_balancer()" replaced it with
nohz_balance_enter_idle(cpu), and removed it on exit, there was nothing
to replace for the current code.
Knowing this patch was considered "buggy" instead of just not moving it
(and forgetting about it), I did the change to remind myself to talk
about it :-)
My question is now, is there any reason to keep that call there? Or can
we just remove it as well.
-- Steve
>
> Regards,
> Charles
>
> On 10/30/2012 04:27 AM, Steven Rostedt wrote:
> ［snipped］
> > @@ -573,7 +573,6 @@ static void tick_nohz_restart_sched_tick(struct
> tick_sched *ts, ktime_t now)
> > tick_do_update_jiffies64(now);
> > update_cpu_load_nohz();
> >
> > - calc_load_exit_idle();
> > touch_softlockup_watchdog();
> > /*
> > * Cancel the scheduled timer and restore the tick
> > @@ -628,6 +627,8 @@ void tick_nohz_idle_exit(void)
> > tick_nohz_stop_idle(cpu, now);
> >
> > if (ts->tick_stopped) {
> > + nohz_balance_enter_idle(cpu);
> > + calc_load_exit_idle();
> > tick_nohz_restart_sched_tick(ts, now);
> > tick_nohz_account_idle_ticks(ts);
> > }
--
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