linux-kernel - [tip:x86/cache] x86/intel_cqm: Modify hot cpu notification handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-8a91dc4e92327b61fbe5941d25e74660e2a44579@git.kernel.org>
Date:	Fri, 18 Dec 2015 13:33:50 -0800
From:	tip-bot for Fenghua Yu <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, mingo@...nel.org, fenghua.yu@...el.com,
	vikas.shivappa@...ux.intel.com, hpa@...or.com,
	linux-kernel@...r.kernel.org
Subject: [tip:x86/cache] x86/intel_cqm:
  Modify hot cpu notification handling

Commit-ID:  8a91dc4e92327b61fbe5941d25e74660e2a44579
Gitweb:     http://git.kernel.org/tip/8a91dc4e92327b61fbe5941d25e74660e2a44579
Author:     Fenghua Yu <fenghua.yu@...el.com>
AuthorDate: Thu, 17 Dec 2015 14:46:06 -0800
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Fri, 18 Dec 2015 13:17:55 -0800

x86/intel_cqm: Modify hot cpu notification handling

From: Vikas Shivappa <vikas.shivappa@...ux.intel.com>

 - 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@...ux.intel.com>
Link: http://lkml.kernel.org/r/1450392376-6397-2-git-send-email-fenghua.yu@intel.com
Signed-off-by: Fenghua Yu <fenghua.yu@...el.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 a316ca9..dd82bc7 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,
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/