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perf/core: Allow reading package events from perf_event_read_local

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Per-package perf events are typically registered with a single CPU only,
however they can be read across all the CPUs within the package.
Currently perf_event_read maps the event CPU according to the topology
information to avoid an unnecessary SMP call, however
perf_event_read_local deals with hard values and rejects a read with a
failure if the CPU is not the one exactly registered. Allow similar
mapping within the perf_event_read_local if the perf event in question
can support this.

This allows users like BPF code to read the package perf events properly
across different CPUs within a package.

Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230913125956.3652667-1-tero.kristo@linux.intel.com
This commit is contained in:
Tero Kristo 2023-09-13 15:59:56 +03:00 committed by Peter Zijlstra
parent 05276d4831
commit 1765bb61bb
1 changed files with 15 additions and 3 deletions
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18
kernel/events/core.c
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@ -4425,6 +4425,9 @@ static int __perf_event_read_cpu(struct perf_event *event, int event_cpu)
{
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();
@ -4527,6 +4530,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
u64 *enabled, u64 *running)
{
unsigned long flags;
int event_oncpu;
int event_cpu;
int ret = 0;
/*
@ -4551,15 +4556,22 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
goto out;
}
/*
* Get the event CPU numbers, and adjust them to local if the event is
* a per-package event that can be read locally
*/
event_oncpu = __perf_event_read_cpu(event, event->oncpu);
event_cpu = __perf_event_read_cpu(event, event->cpu);
/* If this is a per-CPU event, it must be for this CPU */
if (!(event->attach_state & PERF_ATTACH_TASK) &&
event->cpu != smp_processor_id()) {
event_cpu != smp_processor_id()) {
ret = -EINVAL;
goto out;
}
/* If this is a pinned event it must be running on this CPU */
if (event->attr.pinned && event->oncpu != smp_processor_id()) {
if (event->attr.pinned && event_oncpu != smp_processor_id()) {
ret = -EBUSY;
goto out;
}
@ -4569,7 +4581,7 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
* or local to this CPU. Furthermore it means its ACTIVE (otherwise
* oncpu == -1).
*/
if (event->oncpu == smp_processor_id())
if (event_oncpu == smp_processor_id())
event->pmu->read(event);
*value = local64_read(&event->count);