Commit a48a36b3 authored by Kan Liang's avatar Kan Liang Committed by Peter Zijlstra
Browse files

perf: Add PERF_EV_CAP_READ_SCOPE 



Usually, an event can be read from any CPU of the scope. It doesn't need
to be read from the advertised CPU.

Add a new event cap, PERF_EV_CAP_READ_SCOPE. An event of a PMU with
scope can be read from any active CPU in the scope.

Signed-off-by: default avatarKan Liang <kan.liang@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240802151643.1691631-3-kan.liang@linux.intel.com
parent 4ba4f1af

include/linux/perf_event.h

+3 −0
Original line number Diff line number Diff line
@@ -636,10 +636,13 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *, 
 * PERF_EV_CAP_SIBLING: An event with this flag must be a group sibling and

 * cannot be a group leader. If an event with this flag is detached from the

 * group it is scheduled out and moved into an unrecoverable ERROR state.

 * PERF_EV_CAP_READ_SCOPE: A CPU event that can be read from any CPU of the

 * PMU scope where it is active.

 */

#define PERF_EV_CAP_SOFTWARE		BIT(0)

#define PERF_EV_CAP_READ_ACTIVE_PKG	BIT(1)

#define PERF_EV_CAP_SIBLING		BIT(2)

#define PERF_EV_CAP_READ_SCOPE		BIT(3)



#define SWEVENT_HLIST_BITS		8

#define SWEVENT_HLIST_SIZE		(1 << SWEVENT_HLIST_BITS)

kernel/events/core.c

+11 −3
Original line number Diff line number Diff line
@@ -4556,16 +4556,24 @@ struct perf_read_data { 
	int ret;

};



static inline const struct cpumask *perf_scope_cpu_topology_cpumask(unsigned int scope, int cpu);



static int __perf_event_read_cpu(struct perf_event *event, int event_cpu)

{

	int local_cpu = smp_processor_id();

	u16 local_pkg, event_pkg;



	if ((unsigned)event_cpu >= nr_cpu_ids)

		return event_cpu;



	if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {

		int local_cpu = smp_processor_id();

	if (event->group_caps & PERF_EV_CAP_READ_SCOPE) {

		const struct cpumask *cpumask = perf_scope_cpu_topology_cpumask(event->pmu->scope, event_cpu);



		if (cpumask && cpumask_test_cpu(local_cpu, cpumask))

			return local_cpu;

	}



	if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {

		event_pkg = topology_physical_package_id(event_cpu);

		local_pkg = topology_physical_package_id(local_cpu);
@@ -11905,7 +11913,7 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event) 
				if (cpu >= nr_cpu_ids)

					ret = -ENODEV;

				else

					event->cpu = cpu;

					event->event_caps |= PERF_EV_CAP_READ_SCOPE;

			} else {

				ret = -ENODEV;

			}