| Message ID | 20230912124432.3616761-3-tero.kristo@linux.intel.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | perf/x86: Package residency counter improvements | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Tue, Sep 12, 2023 at 03:44:32PM +0300, Tero Kristo wrote: > 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> > --- > kernel/events/core.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 4c72a41f11af..780dde646e8a 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -4528,6 +4528,7 @@ int perf_event_read_local(struct perf_event *event, u64 *value, > { > unsigned long flags; > int ret = 0; > + int event_cpu; > > /* > * Disabling interrupts avoids all counter scheduling (context > @@ -4551,15 +4552,18 @@ int perf_event_read_local(struct perf_event *event, u64 *value, > goto out; > } > > + event_cpu = READ_ONCE(event->oncpu); > + event_cpu = __perf_event_read_cpu(event, event_cpu); What happens with __perf_event_read_cpu() when event_cpu == -1 ? > + > /* 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_cpu != smp_processor_id()) { > ret = -EBUSY; > goto out; > } > @@ -4569,7 +4573,7 @@ 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_cpu == smp_processor_id()) > event->pmu->read(event); > > *value = local64_read(&event->count); > -- > 2.40.1 >
On 12/09/2023 17:04, Peter Zijlstra wrote: > On Tue, Sep 12, 2023 at 03:44:32PM +0300, Tero Kristo wrote: >> 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> >> --- >> kernel/events/core.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/events/core.c b/kernel/events/core.c >> index 4c72a41f11af..780dde646e8a 100644 >> --- a/kernel/events/core.c >> +++ b/kernel/events/core.c >> @@ -4528,6 +4528,7 @@ int perf_event_read_local(struct perf_event *event, u64 *value, >> { >> unsigned long flags; >> int ret = 0; >> + int event_cpu; >> >> /* >> * Disabling interrupts avoids all counter scheduling (context >> @@ -4551,15 +4552,18 @@ int perf_event_read_local(struct perf_event *event, u64 *value, >> goto out; >> } >> >> + event_cpu = READ_ONCE(event->oncpu); >> + event_cpu = __perf_event_read_cpu(event, event_cpu); > What happens with __perf_event_read_cpu() when event_cpu == -1 ? Good question. It looks like I need to add a check against that. Will update and send v2 out. -Tero > >> + >> /* 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_cpu != smp_processor_id()) { >> ret = -EBUSY; >> goto out; >> } >> @@ -4569,7 +4573,7 @@ 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_cpu == smp_processor_id()) >> event->pmu->read(event); >> >> *value = local64_read(&event->count); >> -- >> 2.40.1 >>
diff --git a/kernel/events/core.c b/kernel/events/core.c index 4c72a41f11af..780dde646e8a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4528,6 +4528,7 @@ int perf_event_read_local(struct perf_event *event, u64 *value, { unsigned long flags; int ret = 0; + int event_cpu; /* * Disabling interrupts avoids all counter scheduling (context @@ -4551,15 +4552,18 @@ int perf_event_read_local(struct perf_event *event, u64 *value, goto out; } + event_cpu = READ_ONCE(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_cpu != smp_processor_id()) { ret = -EBUSY; goto out; } @@ -4569,7 +4573,7 @@ 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_cpu == smp_processor_id()) event->pmu->read(event); *value = local64_read(&event->count);
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> --- kernel/events/core.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)