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[RESEND PATCH 1/2] perf/x86/cstate: Allow reading the package statistics from local CPU

Tero Kristo posted 2 patches 2 years, 3 months ago
[RESEND PATCH 1/2] perf/x86/cstate: Allow reading the package statistics from local CPU
Posted by Tero Kristo 2 years, 3 months ago 
The MSR registers for reading the package residency counters are
available on every CPU of the package. To avoid doing unnecessary SMP
calls to read the values for these from the various CPUs inside a
package, allow reading them from any CPU of the package.

Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>
Suggested-by: Kan Liang <kan.liang@intel.com>
---
 arch/x86/events/intel/cstate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/events/intel/cstate.c b/arch/x86/events/intel/cstate.c
index 96fffb2d521d..cbeb6d2bf5b4 100644
--- a/arch/x86/events/intel/cstate.c
+++ b/arch/x86/events/intel/cstate.c
@@ -336,6 +336,9 @@ static int cstate_pmu_event_init(struct perf_event *event)
 		cfg = array_index_nospec((unsigned long)cfg, PERF_CSTATE_PKG_EVENT_MAX);
 		if (!(pkg_msr_mask & (1 << cfg)))
 			return -EINVAL;
+
+		event->event_caps |= PERF_EV_CAP_READ_ACTIVE_PKG;
+
 		event->hw.event_base = pkg_msr[cfg].msr;
 		cpu = cpumask_any_and(&cstate_pkg_cpu_mask,
 				      topology_die_cpumask(event->cpu));
-- 
2.40.1
[PATCHv2 2/2] perf/core: Allow reading package events from perf_event_read_local
Posted by Tero Kristo 2 years, 3 months ago 
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>
---
v2:
  * prevent illegal array access in case event->oncpu == -1
  * split the event->cpu / event->oncpu handling to their own variables

 kernel/events/core.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4c72a41f11af..6b343bac0a71 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4425,6 +4425,9 @@ static int __perf_event_read_cpu(struct perf_event *event, int event_cpu)
 {
 	u16 local_pkg, event_pkg;
 
+	if (event_cpu < 0 || event_cpu >= nr_cpu_ids)
+		return event_cpu;
+
 	if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {
 		int local_cpu = smp_processor_id();
 
@@ -4528,6 +4531,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
 {
 	unsigned long flags;
 	int ret = 0;
+	int event_cpu;
+	int event_oncpu;
 
 	/*
 	 * Disabling interrupts avoids all counter scheduling (context
@@ -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);
-- 
2.40.1
Re: [PATCHv2 2/2] perf/core: Allow reading package events from perf_event_read_local
Posted by Peter Zijlstra 2 years, 2 months ago 
On Wed, Sep 13, 2023 at 03:59:56PM +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>
> ---
> v2:
>   * prevent illegal array access in case event->oncpu == -1
>   * split the event->cpu / event->oncpu handling to their own variables
> 
>  kernel/events/core.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 4c72a41f11af..6b343bac0a71 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4425,6 +4425,9 @@ static int __perf_event_read_cpu(struct perf_event *event, int event_cpu)
>  {
>  	u16 local_pkg, event_pkg;
>  
> +	if (event_cpu < 0 || event_cpu >= nr_cpu_ids)
> +		return event_cpu;

	if ((unsigned)event_cpu >= nr_cpu_ids)
		return event_cpu;

As you could also find at the current __perf_event_read_cpu() callsite.

> +
>  	if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {
>  		int local_cpu = smp_processor_id();
>  
> @@ -4528,6 +4531,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
>  {
>  	unsigned long flags;
>  	int ret = 0;
> +	int event_cpu;
> +	int event_oncpu;

You wrecked the x-mas tree :-)

I'll fix both up.

Thanks!
[tip: perf/core] perf/core: Allow reading package events from perf_event_read_local
Posted by tip-bot2 for Tero Kristo 2 years, 2 months ago 
The following commit has been merged into the perf/core branch of tip:

Commit-ID:     1765bb61bb18a7b81f68806de6e8b8f5000f65bf
Gitweb:        https://git.kernel.org/tip/1765bb61bb18a7b81f68806de6e8b8f5000f65bf
Author:        Tero Kristo <tero.kristo@linux.intel.com>
AuthorDate:    Wed, 13 Sep 2023 15:59:56 +03:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 09 Oct 2023 16:12:22 +02:00

perf/core: Allow reading package events from perf_event_read_local

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
---
 kernel/events/core.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index af56919..708d474 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -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);
[tip: perf/core] perf/x86/cstate: Allow reading the package statistics from local CPU
Posted by tip-bot2 for Tero Kristo 2 years, 2 months ago 
The following commit has been merged into the perf/core branch of tip:

Commit-ID:     05276d4831fe023b6674a72bd6b8c5b39796e690
Gitweb:        https://git.kernel.org/tip/05276d4831fe023b6674a72bd6b8c5b39796e690
Author:        Tero Kristo <tero.kristo@linux.intel.com>
AuthorDate:    Tue, 12 Sep 2023 15:44:31 +03:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 09 Oct 2023 16:12:22 +02:00

perf/x86/cstate: Allow reading the package statistics from local CPU

The MSR registers for reading the package residency counters are
available on every CPU of the package. To avoid doing unnecessary SMP
calls to read the values for these from the various CPUs inside a
package, allow reading them from any CPU of the package.

Suggested-by: Kan Liang <kan.liang@intel.com>
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/20230912124432.3616761-2-tero.kristo@linux.intel.com
---
 arch/x86/events/intel/cstate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/events/intel/cstate.c b/arch/x86/events/intel/cstate.c
index 96fffb2..cbeb6d2 100644
--- a/arch/x86/events/intel/cstate.c
+++ b/arch/x86/events/intel/cstate.c
@@ -336,6 +336,9 @@ static int cstate_pmu_event_init(struct perf_event *event)
 		cfg = array_index_nospec((unsigned long)cfg, PERF_CSTATE_PKG_EVENT_MAX);
 		if (!(pkg_msr_mask & (1 << cfg)))
 			return -EINVAL;
+
+		event->event_caps |= PERF_EV_CAP_READ_ACTIVE_PKG;
+
 		event->hw.event_base = pkg_msr[cfg].msr;
 		cpu = cpumask_any_and(&cstate_pkg_cpu_mask,
 				      topology_die_cpumask(event->cpu));

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