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From: Andi Kleen <andi@firstfloor.org>
To: acme@kernel.org
Cc: peterz@infradead.org, jolsa@kernel.org,
	linux-kernel@vger.kernel.org, mingo@kernel.org,
	Andi Kleen <ak@linux.intel.com>,
	tglx@linutronix.de
Subject: [PATCH 1/8] x86/topology: Add topology_max_smt_threads()
Date: Thu, 19 May 2016 17:09:55 -0700
Message-ID: <1463703002-19686-2-git-send-email-andi@firstfloor.org> (raw)
In-Reply-To: <1463703002-19686-1-git-send-email-andi@firstfloor.org>

From: Andi Kleen <ak@linux.intel.com>

For SMT specific workarounds it is useful to know if SMT is active
on any online CPU in the system. This currently requires a loop
over all online CPUs.

Add a global variable that is updated with the maximum number
of smt threads on any CPU on online/offline, and use it for
topology_max_smt_threads()

The single call is easier to use than a loop.

Not exported to user space because user space already can use
the existing sibling interfaces to find this out.

v2: Code formatting changes and use __ for variable name
v3: Use inlines instead of defines.
Cc: tglx@linutronix.de
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/include/asm/topology.h |  9 +++++++++
 arch/x86/kernel/smpboot.c       | 25 ++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 7f991bd5031b..e346572841a0 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -129,6 +129,14 @@ extern const struct cpumask *cpu_coregroup_mask(int cpu);
 
 extern unsigned int __max_logical_packages;
 #define topology_max_packages()			(__max_logical_packages)
+
+extern int __max_smt_threads;
+
+static inline int topology_max_smt_threads(void)
+{
+	return __max_smt_threads;
+}
+
 int topology_update_package_map(unsigned int apicid, unsigned int cpu);
 extern int topology_phys_to_logical_pkg(unsigned int pkg);
 #else
@@ -136,6 +144,7 @@ extern int topology_phys_to_logical_pkg(unsigned int pkg);
 static inline int
 topology_update_package_map(unsigned int apicid, unsigned int cpu) { return 0; }
 static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; }
+static inline int topology_max_smt_threads(void) { return 1; }
 #endif
 
 static inline void arch_fix_phys_package_id(int num, u32 slot)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 0e4329ed91ef..b753a559ceb9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -105,6 +105,9 @@ static unsigned int max_physical_pkg_id __read_mostly;
 unsigned int __max_logical_packages __read_mostly;
 EXPORT_SYMBOL(__max_logical_packages);
 
+/* Maximum number of SMT threads on any online core */
+int __max_smt_threads __read_mostly;
+
 static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
 {
 	unsigned long flags;
@@ -493,7 +496,7 @@ void set_cpu_sibling_map(int cpu)
 	bool has_mp = has_smt || boot_cpu_data.x86_max_cores > 1;
 	struct cpuinfo_x86 *c = &cpu_data(cpu);
 	struct cpuinfo_x86 *o;
-	int i;
+	int i, threads;
 
 	cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
 
@@ -550,6 +553,10 @@ void set_cpu_sibling_map(int cpu)
 		if (match_die(c, o) && !topology_same_node(c, o))
 			primarily_use_numa_for_topology();
 	}
+
+	threads = cpumask_weight(topology_sibling_cpumask(cpu));
+	if (threads > __max_smt_threads)
+		__max_smt_threads = threads;
 }
 
 /* maps the cpu to the sched domain representing multi-core */
@@ -1441,6 +1448,21 @@ __init void prefill_possible_map(void)
 
 #ifdef CONFIG_HOTPLUG_CPU
 
+/* Recompute SMT state for all CPUs on offline */
+static void recompute_smt_state(void)
+{
+	int max_threads, cpu;
+
+	max_threads = 0;
+	for_each_online_cpu (cpu) {
+		int threads = cpumask_weight(topology_sibling_cpumask(cpu));
+
+		if (threads > max_threads)
+			max_threads = threads;
+	}
+	__max_smt_threads = max_threads;
+}
+
 static void remove_siblinginfo(int cpu)
 {
 	int sibling;
@@ -1465,6 +1487,7 @@ static void remove_siblinginfo(int cpu)
 	c->phys_proc_id = 0;
 	c->cpu_core_id = 0;
 	cpumask_clear_cpu(cpu, cpu_sibling_setup_mask);
+	recompute_smt_state();
 }
 
 static void remove_cpu_from_maps(int cpu)
-- 
2.5.5

  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-20  0:09 Add top down metrics to perf stat Andi Kleen
2016-05-20  0:09 ` Andi Kleen [this message]
2016-06-03 10:52   ` [tip:perf/core] x86/topology: Add topology_max_smt_threads() tip-bot for Andi Kleen
2016-05-20  0:09 ` [PATCH 2/8] perf/x86: Support sysfs files depending on SMT status Andi Kleen
2016-06-03 10:53   ` [tip:perf/core] " tip-bot for Andi Kleen
2016-05-20  0:09 ` [PATCH 3/8] perf/x86/intel: Add Top Down events to Intel Core Andi Kleen
2016-06-03 10:53   ` [tip:perf/core] perf/x86/intel: Add topdown " tip-bot for Andi Kleen
2016-05-20  0:09 ` [PATCH 4/8] perf/x86/intel: Add Top Down events to Intel Atom Andi Kleen
2016-06-03 10:53   ` [tip:perf/core] perf/x86/intel: Add topdown " tip-bot for Andi Kleen
2016-05-20  0:09 ` [PATCH 5/8] perf/x86/intel: Use new topology_max_smt_threads() in HT leak workaround Andi Kleen
2016-06-03 10:54   ` [tip:perf/core] " tip-bot for Andi Kleen
2016-05-20  0:10 ` [PATCH 6/8] perf stat: Avoid fractional digits for integer scales Andi Kleen
2016-05-23 14:36   ` Arnaldo Carvalho de Melo
2016-05-20  0:10 ` [PATCH 7/8] perf stat: Basic support for TopDown in perf stat Andi Kleen
2016-05-23 14:40   ` Arnaldo Carvalho de Melo
2016-05-20  0:10 ` [PATCH 8/8] perf stat: Add computation of TopDown formulas Andi Kleen
  -- strict thread matches above, loose matches on Subject: below --
2016-05-14  1:44 Add top down metrics to perf stat Andi Kleen
2016-05-14  1:44 ` [PATCH 1/8] x86/topology: Add topology_max_smt_threads() Andi Kleen

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