[PATCH 10/10] perf sched timehist: Show callchains for idle stat

[Namhyung Kim <namhyung@kernel.org>]

When --idle-hist option is used with --summary, it now shows idle stats
with callchains like below:

  Idle stats by callchain:
    CPU  0:   902.195  msec
    Idle time (msec)     Count  Callchains
    ----------------  --------  --------------------------------------------------
             370.589        69  futex_wait_queue_me <- futex_wait <- do_futex <- sys_futex <- entry_SYSCALL_64_fastpath
             178.799        17  worker_thread <- kthread <- ret_from_fork
             128.352        17  schedule_timeout <- rcu_gp_kthread <- kthread <- ret_from_fork
             125.111        19  schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- poll_schedule_timeout <- do_select <- core_sys_select
              71.599        50  schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- poll_schedule_timeout <- do_sys_poll <- sys_poll
              23.146         1  rcu_gp_kthread <- kthread <- ret_from_fork
               4.510         1  schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- ep_poll <- sys_epoll_wait <- do_syscall_64
               0.085         1  schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- poll_schedule_timeout <- do_sys_poll <- do_restart_poll
  ...

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/builtin-sched.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 7a5a497d9fa2..acd8ed5af438 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -2436,6 +2436,9 @@ static int timehist_sched_change_event(struct perf_tool *tool,
 				goto out;
 
 			timehist_update_runtime_stats(last_tr, t, tprev);
+			if (itr->cursor.nr)
+				callchain_append(&itr->callchain, &itr->cursor,
+						 t - tprev);
 
 			itr->last_thread = NULL;
 		}
@@ -2546,6 +2549,60 @@ static int show_deadthread_runtime(struct thread *t, void *priv)
 	return __show_thread_runtime(t, priv);
 }
 
+static size_t callchain__fprintf_folded(FILE *fp, struct callchain_node *node)
+{
+	const char *sep = " <- ";
+	struct callchain_list *chain;
+	size_t ret = 0;
+	char bf[1024];
+	bool first;
+
+	if (node == NULL)
+		return 0;
+
+	ret = callchain__fprintf_folded(fp, node->parent);
+	first = (ret == 0);
+
+	list_for_each_entry(chain, &node->val, list) {
+		if (chain->ip >= PERF_CONTEXT_MAX)
+			continue;
+		if (chain->ms.sym && chain->ms.sym->ignore)
+			continue;
+		ret += fprintf(fp, "%s%s", first ? "" : sep,
+			       callchain_list__sym_name(chain, bf, sizeof(bf),
+							false));
+		first = false;
+	}
+
+	return ret;
+}
+
+static size_t timehist_print_idlehist_callchain(struct rb_root *root)
+{
+	size_t ret = 0;
+	FILE *fp = stdout;
+	struct callchain_node *chain;
+	struct rb_node *rb_node = rb_first(root);
+
+	printf("  %16s  %8s  %s\n", "Idle time (msec)", "Count", "Callchains");
+	printf("  %.16s  %.8s  %.50s\n", graph_dotted_line, graph_dotted_line,
+	       graph_dotted_line);
+
+	while (rb_node) {
+		chain = rb_entry(rb_node, struct callchain_node, rb_node);
+		rb_node = rb_next(rb_node);
+
+		ret += fprintf(fp, "  ");
+		print_sched_time(chain->hit, 12);
+		ret += 16;  /* print_sched_time returns 2nd arg + 4 */
+		ret += fprintf(fp, " %8d  ", chain->count);
+		ret += callchain__fprintf_folded(fp, chain);
+		ret += fprintf(fp, "\n");
+	}
+
+	return ret;
+}
+
 static void timehist_print_summary(struct perf_sched *sched,
 				   struct perf_session *session)
 {
@@ -2604,6 +2661,35 @@ static void timehist_print_summary(struct perf_sched *sched,
 			printf("    CPU %2d idle entire time window\n", i);
 	}
 
+	if (sched->idle_hist && symbol_conf.use_callchain) {
+		callchain_param.mode  = CHAIN_FOLDED;
+		callchain_param.value = CCVAL_PERIOD;
+
+		callchain_register_param(&callchain_param);
+
+		printf("\nIdle stats by callchain:\n");
+		for (i = 0; i < idle_max_cpu; ++i) {
+			struct idle_thread_runtime *itr;
+
+			t = idle_threads[i];
+			if (!t)
+				continue;
+
+			itr = thread__priv(t);
+			if (itr == NULL)
+				continue;
+
+			callchain_param.sort(&itr->sorted_root, &itr->callchain,
+					     0, &callchain_param);
+
+			printf("  CPU %2d:", i);
+			print_sched_time(itr->tr.total_run_time, 6);
+			printf(" msec\n");
+			timehist_print_idlehist_callchain(&itr->sorted_root);
+			printf("\n");
+		}
+	}
+
 	printf("\n"
 	       "    Total number of unique tasks: %" PRIu64 "\n"
 	       "Total number of context switches: %" PRIu64 "\n"
-- 
2.10.1