Messages in this thread | | | Date | Tue, 8 Nov 2022 17:16:11 +0100 (CET) | From | Anna-Maria Behnsen <> | Subject | Re: [PATCH v4 14/16] timer: Implement the hierarchical pull model |
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On Mon, 7 Nov 2022, Frederic Weisbecker wrote:
> On Fri, Nov 04, 2022 at 03:57:35PM +0100, Anna-Maria Behnsen wrote: > > @@ -1859,6 +1863,36 @@ void forward_and_idle_timer_bases(unsigned long basej, u64 basem, > > */ > > is_idle = time_after(nextevt, basej + 1); > > > > + if (is_idle) { > > + u64 next_tmigr; > > + > > + next_tmigr = tmigr_cpu_deactivate(tevt->global); > > + > > + tevt->global = KTIME_MAX; > > + > > + /* > > + * If CPU is the last going idle in timer migration > > + * hierarchy, make sure CPU will wake up in time to handle > > + * remote timers. next_tmigr == KTIME_MAX if other CPUs are > > + * still active. > > + */ > > + if (next_tmigr < tevt->local) { > > + u64 tmp; > > + > > + /* If we missed a tick already, force 0 delta */ > > + if (next_tmigr < basem) > > + next_tmigr = basem; > > + > > + tmp = div_u64(next_tmigr - basem, TICK_NSEC); > > + > > + nextevt = basej + (unsigned long)tmp; > > + tevt->local = next_tmigr; > > + is_idle = time_after(nextevt, basej + 1); > > + } else { > > + nextevt = nextevt_local; > > That else part look unecessary.
Yes, you are right. I will add a comment instead. Maybe someone wants to improve it and then requires the proper nextevt...
> > + } > > + } > > + > > /* We need to mark both bases in sync */ > > base_local->is_idle = base_global->is_idle = is_idle; > > Do we still need to maintain base_global->is_idle ?
is_idle information is required in trigger_dyntick_cpu(). I made a mistake with the hunk in trigger_dyntick_cpu() introduced in this patch. Because after this patch, global timers are still enqueued on any CPU because crystallball still exists. trigger_dyntick_cpu() is also required for non pinned timers. I need to move the hunk of trigger_dyntick_cpu() into the last patch of the queue where crystallball is removed during enqueue and there update also this line. Then I will drop the update of base_global->is_idle in timer_clear_idle() as well.
Sorry. This went wrong during splitting and folding the queue back and forwards...
> (I'm going to do daily reviews on this patch because it's quite dense :)
Thanks! I try to answer your questions fast. Let me know when you are done or when you need an updated version for further review :)
Thanks,
Anna-Maria
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