perf_counter tools: Give perf top inherit option

Currently, perf top -p only tracks the pid provided, which isn't very useful
for watching forky loads, so give it an inherit option.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1248165036.9795.10.camel@marge.simson.net>

tools/perf/builtin-top.c

@@ -58,6 +58,7 @@ static u64			count_filter			=  5;
 static int			print_entries			= 15;
 
 static int			target_pid			= -1;
+static int			inherit				=  0;
 static int			profile_cpu			= -1;
 static int			nr_cpus				=  0;
 static unsigned int		realtime_prio			=  0;
@@ -549,7 +550,7 @@ int group_fd;
 static void start_counter(int i, int counter)
 {
 	struct perf_counter_attr *attr;
-	unsigned int cpu;
+	int cpu;
 
 	cpu = profile_cpu;
 	if (target_pid == -1 && profile_cpu == -1)
@@ -559,6 +560,7 @@ static void start_counter(int i, int counter)
 
 	attr->sample_type	= PERF_SAMPLE_IP | PERF_SAMPLE_TID;
 	attr->freq		= freq;
+	attr->inherit		= (cpu < 0) && inherit;
 
 try_again:
 	fd[i][counter] = sys_perf_counter_open(attr, target_pid, cpu, group_fd, 0);
@@ -685,6 +687,8 @@ static const struct option options[] = {
 		    "only display functions with more events than this"),
 	OPT_BOOLEAN('g', "group", &group,
 			    "put the counters into a counter group"),
+	OPT_BOOLEAN('i', "inherit", &inherit,
+		    "child tasks inherit counters"),
 	OPT_STRING('s', "sym-filter", &sym_filter, "pattern",
 		    "only display symbols matchig this pattern"),
 	OPT_BOOLEAN('z', "zero", &zero,