perf tools: Add the ability to specify list of cpus to monitor

This patch adds a -C option to stat, record, top to designate a list of CPUs to
monitor. CPUs can be specified as a comma-separated list or ranges, no space
allowed.

Examples:
$ perf record -a -C0-1,4-7 sleep 1
$ perf top -C0-4
$ perf stat -a -C1,2,3,4 sleep 1

With perf record in per-thread mode with inherit mode on, samples are collected
only when the thread runs on the designated CPUs.

The -C option does not turn on system-wide mode automatically.

Cc: David S. Miller <davem@davemloft.net>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <4bff9496.d345d80a.41fe.7b00@mx.google.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 9a39ca3c3ac..a6b4d44f950 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -69,7 +69,7 @@ static struct perf_event_attr default_attrs[] = {
 };
 
 static bool			system_wide			=  false;
-static unsigned int		nr_cpus				=  0;
+static int			nr_cpus				=  0;
 static int			run_idx				=  0;
 
 static int			run_count			=  1;
@@ -82,6 +82,7 @@ static int			thread_num			=  0;
 static pid_t			child_pid			= -1;
 static bool			null_run			=  false;
 static bool			big_num				=  false;
+static const char		*cpu_list;
 
 
 static int			*fd[MAX_NR_CPUS][MAX_COUNTERS];
@@ -158,7 +159,7 @@ static int create_perf_stat_counter(int counter)
 				    PERF_FORMAT_TOTAL_TIME_RUNNING;
 
 	if (system_wide) {
-		unsigned int cpu;
+		int cpu;
 
 		for (cpu = 0; cpu < nr_cpus; cpu++) {
 			fd[cpu][counter][0] = sys_perf_event_open(attr,
@@ -208,7 +209,7 @@ static inline int nsec_counter(int counter)
 static void read_counter(int counter)
 {
 	u64 count[3], single_count[3];
-	unsigned int cpu;
+	int cpu;
 	size_t res, nv;
 	int scaled;
 	int i, thread;
@@ -542,6 +543,8 @@ static const struct option options[] = {
 		    "null run - dont start any counters"),
 	OPT_BOOLEAN('B', "big-num", &big_num,
 		    "print large numbers with thousands\' separators"),
+	OPT_STRING('C', "cpu", &cpu_list, "cpu",
+		    "list of cpus to monitor in system-wide"),
 	OPT_END()
 };
 
@@ -566,10 +569,13 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used)
 	}
 
 	if (system_wide)
-		nr_cpus = read_cpu_map();
+		nr_cpus = read_cpu_map(cpu_list);
 	else
 		nr_cpus = 1;
 
+	if (nr_cpus < 1)
+		usage_with_options(stat_usage, options);
+
 	if (target_pid != -1) {
 		target_tid = target_pid;
 		thread_num = find_all_tid(target_pid, &all_tids);