[PATCH 2/9] x86/intel_rapl: Modify hot cpu notification handling for RAPL

[Vikas Shivappa]

This patch modifies the hot cpu notification handling in
Intel Running Average Power Limit(RAPL) driver.

 - to add a cpu reader to the rapl_cpumask(which has one cpu per package
     set) it uses the existing package<->core map instead of looping
 through all cpus in rapl_cpumask.
 - to search for the next online sibling during hot cpu exit, it uses
 the same mapping instead of looping all online cpus. In
 large systems with large number of cpus the time taken to loop may be
 expensive and also the time increase linearly.

Signed-off-by: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/perf_event_intel_rapl.c | 30 +++++++++++++----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 358c54a..d6ef46a 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -524,18 +524,17 @@ static struct pmu rapl_pmu_class = {
 static void rapl_cpu_exit(int cpu)
 {
 	struct rapl_pmu *pmu = per_cpu(rapl_pmu, cpu);
-	int i, phys_id = topology_physical_package_id(cpu);
+	static cpumask_t tmp;
 	int target = -1;
+	int i;
 
 	/* find a new cpu on same package */
-	for_each_online_cpu(i) {
-		if (i == cpu)
-			continue;
-		if (phys_id == topology_physical_package_id(i)) {
-			target = i;
-			break;
-		}
-	}
+	cpumask_and(&tmp, topology_core_cpumask(cpu), cpu_online_mask);
+	cpumask_clear_cpu(cpu, &tmp);
+	i = cpumask_any(&tmp);
+	if (i < nr_cpu_ids)
+		target = i;
+
 	/*
 	 * clear cpu from cpumask
 	 * if was set in cpumask and still some cpu on package,
@@ -557,15 +556,12 @@ static void rapl_cpu_exit(int cpu)
 
 static void rapl_cpu_init(int cpu)
 {
-	int i, phys_id = topology_physical_package_id(cpu);
+	static cpumask_t tmp;
 
-	/* check if phys_is is already covered */
-	for_each_cpu(i, &rapl_cpu_mask) {
-		if (phys_id == topology_physical_package_id(i))
-			return;
-	}
-	/* was not found, so add it */
-	cpumask_set_cpu(cpu, &rapl_cpu_mask);
+	/* check if cpu's package is already covered.If not, add it.*/
+	cpumask_and(&tmp, &rapl_cpu_mask, topology_core_cpumask(cpu));
+	if (cpumask_empty(&tmp))
+		cpumask_set_cpu(cpu, &rapl_cpu_mask);
 }
 
 static __init void rapl_hsw_server_quirk(void)
-- 
1.9.1

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