linux-kernel - [PATCH 02/11] x86/intel_rapl: Modify hot cpu notification handling

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Date:	Wed,  9 Sep 2015 12:24:53 -0700
From:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To:	vikas.shivappa@...el.com
Cc:	vikas.shivappa@...ux.intel.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...nel.org, tj@...nel.org, peterz@...radead.org,
	matt.fleming@...el.com, will.auld@...el.com,
	h.peter.anvin@...el.com, glenn.p.williamson@...el.com,
	kanaka.d.juvva@...el.com, bruce.schlobohm@...el.com
Subject: [PATCH 02/11] x86/intel_rapl: Modify hot cpu notification handling

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

 - In rapl_cpu_exit, use 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@...ux.intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel_rapl.c | 35 ++++++++++++++---------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 5cbd4e6..3f3fb4c 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -132,6 +132,12 @@ static struct pmu rapl_pmu_class;
 static cpumask_t rapl_cpu_mask;
 static int rapl_cntr_mask;
 
+/*
+ * Temporary cpumask used during hot cpu notificaiton handling. The usage
+ * is serialized by hot cpu locks.
+ */
+static cpumask_t tmp_cpumask;
+
 static DEFINE_PER_CPU(struct rapl_pmu *, rapl_pmu);
 static DEFINE_PER_CPU(struct rapl_pmu *, rapl_pmu_to_free);
 
@@ -523,18 +529,16 @@ 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);
 	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_cpumask, topology_core_cpumask(cpu), cpu_online_mask);
+	cpumask_clear_cpu(cpu, &tmp_cpumask);
+	i = cpumask_any(&tmp_cpumask);
+	if (i < nr_cpu_ids)
+		target = i;
+
 	/*
 	 * clear cpu from cpumask
 	 * if was set in cpumask and still some cpu on package,
@@ -556,15 +560,10 @@ static void rapl_cpu_exit(int cpu)
 
 static void rapl_cpu_init(int cpu)
 {
-	int i, phys_id = topology_physical_package_id(cpu);
-
-	/* 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_cpumask, &rapl_cpu_mask, topology_core_cpumask(cpu));
+	if (cpumask_empty(&tmp_cpumask))
+		cpumask_set_cpu(cpu, &rapl_cpu_mask);
 }
 
 static __init void rapl_hsw_server_quirk(void)
-- 
1.9.1

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