[PATCH v3 1/3] perf: add cpu__max_present_cpu()

[Jan Stancek <jstancek@redhat.com>]

Similar to cpu__max_cpu() (which returns max possible CPU),
returns max present CPU.

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
 tools/perf/util/cpumap.c | 22 ++++++++++++++++++++++
 tools/perf/util/cpumap.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 2c0b52264a46..8c7504939113 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -9,6 +9,7 @@
 #include "asm/bug.h"
 
 static int max_cpu_num;
+static int max_present_cpu_num;
 static int max_node_num;
 static int *cpunode_map;
 
@@ -442,6 +443,7 @@ static void set_max_cpu_num(void)
 
 	/* set up default */
 	max_cpu_num = 4096;
+	max_present_cpu_num = 4096;
 
 	mnt = sysfs__mountpoint();
 	if (!mnt)
@@ -455,6 +457,17 @@ static void set_max_cpu_num(void)
 	}
 
 	ret = get_max_num(path, &max_cpu_num);
+	if (ret)
+		goto out;
+
+	/* get the highest present cpu number for a sparse allocation */
+	ret = snprintf(path, PATH_MAX, "%s/devices/system/cpu/present", mnt);
+	if (ret == PATH_MAX) {
+		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
+		goto out;
+	}
+
+	ret = get_max_num(path, &max_present_cpu_num);
 
 out:
 	if (ret)
@@ -505,6 +518,15 @@ int cpu__max_cpu(void)
 	return max_cpu_num;
 }
 
+int cpu__max_present_cpu(void)
+{
+	if (unlikely(!max_present_cpu_num))
+		set_max_cpu_num();
+
+	return max_present_cpu_num;
+}
+
+
 int cpu__get_node(int cpu)
 {
 	if (unlikely(cpunode_map == NULL)) {
diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
index 06bd689f5989..1a0549af8f5c 100644
--- a/tools/perf/util/cpumap.h
+++ b/tools/perf/util/cpumap.h
@@ -62,6 +62,7 @@ static inline bool cpu_map__empty(const struct cpu_map *map)
 
 int cpu__max_node(void);
 int cpu__max_cpu(void);
+int cpu__max_present_cpu(void);
 int cpu__get_node(int cpu);
 
 int cpu_map__build_map(struct cpu_map *cpus, struct cpu_map **res,
-- 
1.8.3.1