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perf: Add PERF_EV_CAP_READ_SCOPE

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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: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240802151643.1691631-3-kan.liang@linux.intel.com
This commit is contained in:
Kan Liang 2024-08-02 08:16:38 -07:00 committed by Peter Zijlstra
parent 4ba4f1afb6
commit a48a36b316
2 changed files with 14 additions and 3 deletions
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3
include/linux/perf_event.h
View File

@ -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)

14
kernel/events/core.c
View File

@ -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;
}