perfcounters: add task migrations counter
Impact: add new feature, new sw counter
Add a counter that counts the number of cross-CPU migrations a
task is suffering.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 0928709..fb11e35 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -936,6 +936,52 @@
.hw_perf_counter_read = context_switches_perf_counter_read,
};
+static inline u64 get_cpu_migrations(void)
+{
+ return current->se.nr_migrations;
+}
+
+static void cpu_migrations_perf_counter_update(struct perf_counter *counter)
+{
+ u64 prev, now;
+ s64 delta;
+
+ prev = atomic64_read(&counter->hw.prev_count);
+ now = get_cpu_migrations();
+
+ atomic64_set(&counter->hw.prev_count, now);
+
+ delta = now - prev;
+ if (WARN_ON_ONCE(delta < 0))
+ delta = 0;
+
+ atomic64_add(delta, &counter->count);
+}
+
+static void cpu_migrations_perf_counter_read(struct perf_counter *counter)
+{
+ cpu_migrations_perf_counter_update(counter);
+}
+
+static void cpu_migrations_perf_counter_enable(struct perf_counter *counter)
+{
+ /*
+ * se.nr_migrations is a per-task value already,
+ * so we dont have to clear it on switch-in.
+ */
+}
+
+static void cpu_migrations_perf_counter_disable(struct perf_counter *counter)
+{
+ cpu_migrations_perf_counter_update(counter);
+}
+
+static const struct hw_perf_counter_ops perf_ops_cpu_migrations = {
+ .hw_perf_counter_enable = cpu_migrations_perf_counter_enable,
+ .hw_perf_counter_disable = cpu_migrations_perf_counter_disable,
+ .hw_perf_counter_read = cpu_migrations_perf_counter_read,
+};
+
static const struct hw_perf_counter_ops *
sw_perf_counter_init(struct perf_counter *counter)
{
@@ -951,6 +997,9 @@
case PERF_COUNT_CONTEXT_SWITCHES:
hw_ops = &perf_ops_context_switches;
break;
+ case PERF_COUNT_CPU_MIGRATIONS:
+ hw_ops = &perf_ops_cpu_migrations;
+ break;
default:
break;
}