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[PATCH 01/11] x86/intel_cqm: Modify hot cpu notification handling

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 - In cqm_pick_event_reader, use the existing package<->core map instead
 of looping through all cpus in cqm_cpumask.

 - In intel_cqm_cpu_exit, use the same map instead of looping through
 all online cpus. In large systems with large number of cpus the time
 taken to loop may be expensive and also the time increases linearly.

Signed-off-by: Vikas Shivappa <vikas.shivappa@linux.intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel_cqm.c | 34 +++++++++++++++---------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_cqm.c b/arch/x86/kernel/cpu/perf_event_intel_cqm.c
index 377e8f8..93e54ad 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_cqm.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_cqm.c
@@ -62,6 +62,12 @@ static LIST_HEAD(cache_groups);
  */
 static cpumask_t cqm_cpumask;
 
+/*
+ * Temporary cpumask used during hot cpu notificaiton handling. The usage
+ * is serialized by hot cpu locks.
+ */
+static cpumask_t tmp_cpumask;
+
 #define RMID_VAL_ERROR		(1ULL << 63)
 #define RMID_VAL_UNAVAIL	(1ULL << 62)
 
@@ -1244,15 +1250,13 @@ static struct pmu intel_cqm_pmu = {
 
 static inline void cqm_pick_event_reader(int cpu)
 {
-	int phys_id = topology_physical_package_id(cpu);
-	int i;
+	cpumask_and(&tmp_cpumask, &cqm_cpumask, topology_core_cpumask(cpu));
 
-	for_each_cpu(i, &cqm_cpumask) {
-		if (phys_id == topology_physical_package_id(i))
-			return;	/* already got reader for this socket */
-	}
-
-	cpumask_set_cpu(cpu, &cqm_cpumask);
+	/*
+	 * Pick a reader if there isn't one already.
+	 */
+	if (cpumask_empty(&tmp_cpumask))
+		cpumask_set_cpu(cpu, &cqm_cpumask);
 }
 
 static void intel_cqm_cpu_starting(unsigned int cpu)
@@ -1270,7 +1274,6 @@ static void intel_cqm_cpu_starting(unsigned int cpu)
 
 static void intel_cqm_cpu_exit(unsigned int cpu)
 {
-	int phys_id = topology_physical_package_id(cpu);
 	int i;
 
 	/*
@@ -1279,15 +1282,12 @@ static void intel_cqm_cpu_exit(unsigned int cpu)
 	if (!cpumask_test_and_clear_cpu(cpu, &cqm_cpumask))
 		return;
 
-	for_each_online_cpu(i) {
-		if (i == cpu)
-			continue;
+	cpumask_and(&tmp_cpumask, topology_core_cpumask(cpu), cpu_online_mask);
+	cpumask_clear_cpu(cpu, &tmp_cpumask);
+	i = cpumask_any(&tmp_cpumask);
 
-		if (phys_id == topology_physical_package_id(i)) {
-			cpumask_set_cpu(i, &cqm_cpumask);
-			break;
-		}
-	}
+	if (i < nr_cpu_ids)
+		cpumask_set_cpu(i, &cqm_cpumask);
 }
 
 static int intel_cqm_cpu_notifier(struct notifier_block *nb,
-- 
1.9.1

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Thread

[PATCH V14 0/9] Intel cache allocation and Hot cpu handling changes to cqm, rapl Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 10/11] x86,cgroup/intel_rdt : Add intel_rdt cgroup documentation Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 05/11] x86/intel_rdt: Add Class of service management Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 02/11] x86/intel_rapl: Modify hot cpu notification handling Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 03/11] x86/intel_rdt: Cache Allocation documentation Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 07/11] x86/intel_rdt: Implement scheduling support for Intel RDT Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 08/11] x86/intel_rdt: Hot cpu support for Cache Allocation Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 06/11] x86/intel_rdt: Add L3 cache capacity bitmask management Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 11/11] x86,cgroup/intel_rdt : Add a cgroup interface to manage Intel cache allocation Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 01/11] x86/intel_cqm: Modify hot cpu notification handling Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 04/11] x86/intel_rdt: Add support for Cache Allocation detection Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200
  [PATCH 09/11] x86/intel_rdt: Intel haswell Cache Allocation enumeration Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2015-09-09 21:30 +0200

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