On 08/06/16 22:12, David Carrillo-Cisneros wrote:
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 34049cc..77f1bd3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3333,6 +3333,26 @@ struct perf_read_data {
int ret;
};
+static int find_cpu_to_read(struct perf_event *event)
+{
+ bool active = event->state == PERF_EVENT_STATE_ACTIVE;
+ int event_cpu = event->oncpu, local_cpu = smp_processor_id();
+ u16 local_pkg, event_pkg;
+
+ if (!active)
+ return -1;
+
+ 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);
+
+ if (event_pkg == local_pkg)
+ return local_cpu;
+ }
+
+ return event_cpu;
+}
+
/*
* Cross CPU call to read the hardware event
*/
@@ -3454,19 +3474,17 @@ u64 perf_event_read_local(struct perf_event *event)
static int perf_event_read(struct perf_event *event, bool group)
{
- int ret = 0;
+ int ret = 0, cpu_to_read;
- /*
- * If event is enabled and currently active on a CPU, update the
- * value in the event structure:
- */
- if (event->state == PERF_EVENT_STATE_ACTIVE) {
+ cpu_to_read = find_cpu_to_read(event);
+
+ if (cpu_to_read >= 0) {
struct perf_read_data data = {
.event = event,
.group = group,
.ret = 0,
};
- ret = smp_call_function_single(event->oncpu,
+ ret = smp_call_function_single(cpu_to_read,
__perf_event_read, &data, 1);
ret = ret ? : data.ret;
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
I would like to suggest a small change to this patch. I think the check
on PERF_EVENT_STATE_ACTIVE should be retained in the perf_event_read()
function. The new function should assume that the event is active. I
find this more readable since the next check in function
perf_event_read() is on PERF_EVENT_STATE_INACTIVE.
Diff below:
+static int find_cpu_to_read(struct perf_event *event)
+{
+ int event_cpu = event->oncpu, local_cpu = smp_processor_id();
+ u16 local_pkg, event_pkg;
+
+ 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);
+
+ if (event_pkg == local_pkg)
+ return local_cpu;
+ }
+
+ return event_cpu;
+}
+
/*
* Cross CPU call to read the hardware event
*/
@@ -3477,17 +3493,15 @@ static int perf_event_read(struct perf_event
*event, bool group)
{
int ret = 0;
- /*
- * If event is enabled and currently active on a CPU, update the
- * value in the event structure:
- */
- if (event->state == PERF_EVENT_STATE_ACTIVE) {
+ if (event->state == PERF_EVENT_STATE_ACTIVE) {
+ int cpu_to_read = find_cpu_to_read(event);
+
struct perf_read_data data = {
.event = event,
.group = group,
.ret = 0,
};
- ret = smp_call_function_single(event->oncpu,
+ ret = smp_call_function_single(cpu_to_read,
__perf_event_read,
&data, 1);
ret = ret ? : data.ret;
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
