perf sched timehist: Add support for filtering on CPU

Allow user to limit output to one or more CPUs. Really helpful on
systems with a large number of cpus.

Committer testing:

# perf sched record -a sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 1.765 MB perf.data (1412 samples) ]
[root@quaco ~]# perf sched timehist | head
Samples do not have callchains.
time cpu task name wait time sch delay run time
[tid/pid] (msec) (msec) (msec)
--------------- ------ ------------------------------ --------- --------- ---------
66307.802686 [0000] perf[13086] 0.000 0.000 0.000
66307.802700 [0000] migration/0[12] 0.000 0.001 0.014
66307.802766 [0001] perf[13086] 0.000 0.000 0.000
66307.802774 [0001] migration/1[15] 0.000 0.001 0.007
66307.802841 [0002] perf[13086] 0.000 0.000 0.000
66307.802849 [0002] migration/2[20] 0.000 0.001 0.008
66307.802913 [0003] perf[13086] 0.000 0.000 0.000
#
# perf sched timehist --cpu 2 | head
Samples do not have callchains.
time cpu task name wait time sch delay run time
[tid/pid] (msec) (msec) (msec)
--------------- ------ ------------------------------ --------- --------- ---------
66307.802841 [0002] perf[13086] 0.000 0.000 0.000
66307.802849 [0002] migration/2[20] 0.000 0.001 0.008
66307.964485 [0002] <idle> 0.000 0.000 161.635
66307.964811 [0002] CPU 0/KVM[3589/3561] 0.000 0.056 0.325
66307.965477 [0002] <idle> 0.325 0.000 0.666
66307.965553 [0002] CPU 0/KVM[3589/3561] 0.666 0.024 0.076
66307.966456 [0002] <idle> 0.076 0.000 0.903
#

Signed-off-by: David Ahern <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-sched.txt

···
 --max-stack::
 	Maximum number of functions to display in backtrace, default 5.
 
+-C=::
+--cpu=::
+	Only show events for the given CPU(s) (comma separated list).
+
 -p=::
 --pid=::
 	Only show events for given process ID (comma separated list).

tools/perf/builtin-sched.c

···
 #define SYM_LEN			129
 #define MAX_PID			1024000
 
+static const char *cpu_list;
+static DECLARE_BITMAP(cpu_bitmap, MAX_NR_CPUS);
+
 struct sched_atom;
 
 struct task_desc {
···
 	char nstr[30];
 	u64 wait_time;
 
+	if (cpu_list && !test_bit(sample->cpu, cpu_bitmap))
+		return;
+
 	timestamp__scnprintf_usec(t, tstr, sizeof(tstr));
 	printf("%15s [%04d] ", tstr, sample->cpu);
 
···
 	if (IS_ERR(session))
 		return PTR_ERR(session);
 
+	if (cpu_list) {
+		err = perf_session__cpu_bitmap(session, cpu_list, cpu_bitmap);
+		if (err < 0)
+			goto out;
+	}
+
 	evlist = session->evlist;
 
 	symbol__init(&session->header.env);
···
 		   "analyze events only for given process id(s)"),
 	OPT_STRING('t', "tid", &symbol_conf.tid_list_str, "tid[,tid...]",
 		   "analyze events only for given thread id(s)"),
+	OPT_STRING('C', "cpu", &cpu_list, "cpu", "list of cpus to profile"),
 	OPT_PARENT(sched_options)
 	};