perf cgroup: Clean up perf_cgroup_create()

- Use kzalloc() to replace kmalloc() + memset().

- Remove redundant initialization, since alloc_percpu() returns
  zero-filled percpu memory.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4D6F347E.2010806@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -7346,26 +7346,17 @@ static struct cgroup_subsys_state *perf_cgroup_create(
 	struct cgroup_subsys *ss, struct cgroup *cont)
 {
 	struct perf_cgroup *jc;
-	struct perf_cgroup_info *t;
-	int c;
 
-	jc = kmalloc(sizeof(*jc), GFP_KERNEL);
+	jc = kzalloc(sizeof(*jc), GFP_KERNEL);
 	if (!jc)
 		return ERR_PTR(-ENOMEM);
 
-	memset(jc, 0, sizeof(*jc));
-
 	jc->info = alloc_percpu(struct perf_cgroup_info);
 	if (!jc->info) {
 		kfree(jc);
 		return ERR_PTR(-ENOMEM);
 	}
 
-	for_each_possible_cpu(c) {
-		t = per_cpu_ptr(jc->info, c);
-		t->time = 0;
-		t->timestamp = 0;
-	}
 	return &jc->css;
 }