perf sched timehist: Show callchains for idle stat

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
  ...

Committer notes:

Extra testing:

  # uname -a
  Linux jouet 4.8.8-300.fc25.x86_64 #1 SMP Tue Nov 15 18:10:06 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

1) Run 'perf sched record -g'

2) Run 'perf sched timehist --idle --summary'

<SNIP>
  Idle stats by callchain:
  CPU  0: 13456.840 msec
  Idle time (msec) Count Callchains
  ---------------- ----- --------------------------------------------------
          5386.637  3283 schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- poll_schedule_timeout <- do_sys_poll <- sys_poll
          2750.238  2299 futex_wait_queue_me <- futex_wait <- do_futex <- sys_futex <- do_syscall_64
          1275.672  1287 schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- ep_poll <- sys_epoll_wait <- entry_SYSCALL_64_fastpath
           936.322   452 worker_thread <- kthread <- ret_from_fork
           741.311   385 rcu_nocb_kthread <- kthread <- ret_from_fork
           729.385   248 schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- poll_schedule_timeout <- do_sys_poll <- sys_ppoll
           365.386   229 irq_thread <- kthread <- ret_from_fork
           338.934   265 futex_wait_queue_me <- futex_wait <- do_futex <- sys_futex <- entry_SYSCALL_64_fastpath
           219.488   201 schedule_timeout <- rcu_gp_kthread <- kthread <- ret_from_fork
           186.839   410 schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- ep_poll <- sys_epoll_wait <- do_syscall_64
           142.541    59 kvm_vcpu_block <- kvm_arch_vcpu_ioctl_run <- kvm_vcpu_ioctl <- do_vfs_ioctl <- sys_ioctl
            83.887    92 smpboot_thread_fn <- kthread <- ret_from_fork
            62.722    96 do_exit <- do_group_exit <- 0x2a5594 <- entry_SYSCALL_64_fastpath
            47.894    83 pipe_wait <- pipe_read <- __vfs_read <- vfs_read <- sys_read
            46.554    61 rcu_gp_kthread <- kthread <- ret_from_fork
            34.337    21 schedule_timeout <- intel_fbc_work_fn <- process_one_work <- worker_thread <- kthread
            29.521    14 schedule_hrtimeout_range_clock <- schedule_hrtimeout_range <- poll_schedule_timeout <- do_select <- core_sys_select
            20.274    10 schedule_timeout <- io_schedule_timeout <- bit_wait_io <- __wait_on_bit <- out_of_line_wait_on_bit
            15.085    55 schedule_timeout <- unix_stream_read_generic <- unix_stream_recvmsg <- sock_recvmsg <- SYSC_recvfrom
<SNIP>

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: David Ahern <dsahern@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20161208144755.16673-7-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-sched.c

@@ -2448,6 +2448,9 @@ static int timehist_sched_change_event(struct perf_tool *tool,
 			last_tr->dt_wait = 0;
 			last_tr->dt_delay = 0;
 
+			if (itr->cursor.nr)
+				callchain_append(&itr->callchain, &itr->cursor, t - tprev);
+
 			itr->last_thread = NULL;
 		}
 	}
@@ -2557,6 +2560,60 @@ 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)
 {
@@ -2615,6 +2672,35 @@ 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"