On Wed, Nov 12, 2014 at 11:41:09AM +0530, Viresh Kumar wrote:
> On 11 November 2014 22:45, Frederic Weisbecker <fweis...@gmail.com> wrote:
>
> > Here is a summarized list:
> >
> > * Unbound workqueues affinity (to housekeeper)
> > * Unbound timers affinity (to housekeeper)
> > * 1 Hz residual scheduler tick offlining to housekeeper
> > * Fix some scheduler accounting that don't even work with 1 Hz: cpu load
> > accounting, rt_scale, load balancing, etc...
> > * Lighten the syscall path and get rid of cputime accounting + RCU hooks
> > for people who want isolation + fast syscalls and faults.
> > * Work on non-affinable workqueues
> > * Work on non-affinable timers
> > * ...
>
> + spurious interrupts with NOHZ_FULL on all architectures which break
> isolation
> but doesn't get caught with traces. Can be observed with this:
>
> diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
> index 481fa54..91d490d 100644
> --- a/kernel/time/hrtimer.c
> +++ b/kernel/time/hrtimer.c
> @@ -1244,7 +1244,8 @@ void hrtimer_interrupt(struct clock_event_device *dev)
> {
> struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
> ktime_t expires_next, now, entry_time, delta;
> - int i, retries = 0;
> + int i, retries = 0, count = 0;
> + static int total_spurious;
>
> BUG_ON(!cpu_base->hres_active);
> cpu_base->nr_events++;
> @@ -1304,10 +1305,14 @@ void hrtimer_interrupt(struct clock_event_device *dev)
> break;
> }
>
> + count++;
> __run_hrtimer(timer, &basenow);
> }
> }
>
> + if (!count)
> + pr_err("____%s: Totalspurious: %d\n", __func__,
> ++total_spurious);
> +
I'd rather leave that to tracepoints. Like trace_hrtimer_spurious().
Or better yet: have trace_hrtimer_interrupt() which we can compare against
trace_hrtimer_expire_entry/exit() to check if any hrtimer callback have run
in the interrupt. This way we avoid workarounds like the above count.
> /*
> * Store the new expiry value so the migration code can verify
> * against it.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
