linux-kernel - [PATCH v2 4/4] perf: Avoid the percore allocations if HT is not capable

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Date:	Wed, 02 Mar 2011 00:48:25 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 4/4] perf: Avoid the percore allocations if HT is not
 capable

No need to do percore allocations if HT is not capable

Signed-off-by: Lin Ming <ming.m.lin@...el.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c |   23 +++++++++++++++++------
 1 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index e82a7f9..ac1d100 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1089,10 +1089,18 @@ static __initconst const struct x86_pmu core_pmu = {
 	.event_constraints	= intel_core_event_constraints,
 };
 
+static bool ht_capable(void)
+{
+	return boot_cpu_has(X86_FEATURE_HT) && smp_num_siblings > 1;
+}
+
 static int intel_pmu_cpu_prepare(int cpu)
 {
 	struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
 
+	if (!ht_capable())
+		return NOTIFY_OK;
+
 	cpuc->per_core = kzalloc_node(sizeof(struct intel_percore),
 				      GFP_KERNEL, cpu_to_node(cpu));
 	if (!cpuc->per_core)
@@ -1109,6 +1117,15 @@ static void intel_pmu_cpu_starting(int cpu)
 	int core_id = topology_core_id(cpu);
 	int i;
 
+	init_debug_store_on_cpu(cpu);
+	/*
+	 * Deal with CPUs that don't clear their LBRs on power-up.
+	 */
+	intel_pmu_lbr_reset();
+
+	if (!ht_capable())
+		return;
+
 	for_each_cpu(i, topology_thread_cpumask(cpu)) {
 		struct intel_percore *pc = per_cpu(cpu_hw_events, i).per_core;
 
@@ -1121,12 +1138,6 @@ static void intel_pmu_cpu_starting(int cpu)
 
 	cpuc->per_core->core_id = core_id;
 	cpuc->per_core->refcnt++;
-
-	init_debug_store_on_cpu(cpu);
-	/*
-	 * Deal with CPUs that don't clear their LBRs on power-up.
-	 */
-	intel_pmu_lbr_reset();
 }
 
 static void intel_pmu_cpu_dying(int cpu)
-- 
1.7.3





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