Commit 05c9b0cb authored by Sandipan Das's avatar Sandipan Das Committed by Ingo Molnar
Browse files

perf/x86/intel/uncore: Use HRTIMER_MODE_HARD for detecting overflows 



hrtimer handlers can be deferred to softirq context and affect timely
detection of counter overflows. Hence switch to HRTIMER_MODE_HARD.

Disabling and re-enabling IRQs in the hrtimer handler is not required
as pmu->start() and pmu->stop() can no longer intervene while updating
event->hw.prev_count.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarSandipan Das <sandipan.das@amd.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/0ad4698465077225769e8edd5b2c7e8f48f636d5.1744906694.git.sandipan.das@amd.com
parent 4f81cc2d

arch/x86/events/intel/uncore.c

+2 −10
Original line number Diff line number Diff line
@@ -305,17 +305,11 @@ static enum hrtimer_restart uncore_pmu_hrtimer(struct hrtimer *hrtimer) 
{

	struct intel_uncore_box *box;

	struct perf_event *event;

	unsigned long flags;

	int bit;



	box = container_of(hrtimer, struct intel_uncore_box, hrtimer);

	if (!box->n_active || box->cpu != smp_processor_id())

		return HRTIMER_NORESTART;

	/*

	 * disable local interrupt to prevent uncore_pmu_event_start/stop

	 * to interrupt the update process

	 */

	local_irq_save(flags);



	/*

	 * handle boxes with an active event list as opposed to active
@@ -328,8 +322,6 @@ static enum hrtimer_restart uncore_pmu_hrtimer(struct hrtimer *hrtimer) 
	for_each_set_bit(bit, box->active_mask, UNCORE_PMC_IDX_MAX)

		uncore_perf_event_update(box, box->events[bit]);



	local_irq_restore(flags);



	hrtimer_forward_now(hrtimer, ns_to_ktime(box->hrtimer_duration));

	return HRTIMER_RESTART;

}
@@ -337,7 +329,7 @@ static enum hrtimer_restart uncore_pmu_hrtimer(struct hrtimer *hrtimer) 
void uncore_pmu_start_hrtimer(struct intel_uncore_box *box)

{

	hrtimer_start(&box->hrtimer, ns_to_ktime(box->hrtimer_duration),

		      HRTIMER_MODE_REL_PINNED);

		      HRTIMER_MODE_REL_PINNED_HARD);

}



void uncore_pmu_cancel_hrtimer(struct intel_uncore_box *box)
@@ -347,7 +339,7 @@ void uncore_pmu_cancel_hrtimer(struct intel_uncore_box *box) 


static void uncore_pmu_init_hrtimer(struct intel_uncore_box *box)

{

	hrtimer_setup(&box->hrtimer, uncore_pmu_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	hrtimer_setup(&box->hrtimer, uncore_pmu_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);

}



static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type *type,