Commit 833d0252 authored Feb 07, 2025 by Gabriele Monaco Committed by Namhyung Kim Feb 26, 2025

perf ftrace latency: allow to hide empty buckets



Especially while using several buckets, it isn't uncommon to have some
of them empty and reading the histogram may be a bit more complex:

  # perf ftrace latency -a -T mutex_lock --bucket-range 5 --max-latency 200
  #   DURATION     |  COUNT | GRAPH                                  |
       0 -    5 us |  14816 | ###################################### |
       5 -   10 us |   1228 | ###                                    |
      10 -   15 us |    438 | #                                      |
      15 -   20 us |    106 |                                        |
      20 -   25 us |     21 |                                        |
      25 -   30 us |     11 |                                        |
      30 -   35 us |      1 |                                        |
      35 -   40 us |      2 |                                        |
      40 -   45 us |      4 |                                        |
      45 -   50 us |      0 |                                        |
      50 -   55 us |      1 |                                        |
      55 -   60 us |      0 |                                        |
      60 -   65 us |      1 |                                        |
      65 -   70 us |      1 |                                        |
      70 -   75 us |      1 |                                        |
      75 -   80 us |      2 |                                        |
      80 -   85 us |      0 |                                        |
      85 -   90 us |      1 |                                        |
      90 -   95 us |      0 |                                        |
      95 -  100 us |      1 |                                        |
     100 -  105 us |      0 |                                        |
     105 -  110 us |      0 |                                        |
     110 -  115 us |      0 |                                        |
     115 -  120 us |      0 |                                        |
     120 -  125 us |      1 |                                        |
     125 -  130 us |      0 |                                        |
     130 -  135 us |      0 |                                        |
     135 -  140 us |      1 |                                        |
     140 -  145 us |      0 |                                        |
     145 -  150 us |      0 |                                        |
     150 -  155 us |      0 |                                        |
     155 -  160 us |      0 |                                        |
     160 -  165 us |      0 |                                        |
     165 -  170 us |      0 |                                        |
     170 -  175 us |      0 |                                        |
     175 -  180 us |      0 |                                        |
     180 -  185 us |      0 |                                        |
     185 -  190 us |      0 |                                        |
     190 -  195 us |      0 |                                        |
     195 -  200 us |      0 |                                        |
     200 -  ... us |      2 |                                        |

Allow the optional flag --hide-empty to remove buckets with no element
and produce a more compact graph. This feature could be misleading since
there is no clear indication for missing buckets, for this reason it's
disabled by default.

  # perf ftrace latency -a -T mutex_lock --bucket-range 5 --max-latency --hide-empty 200
  #   DURATION     |  COUNT | GRAPH                                  |
       0 -    5 us |  14816 | ###################################### |
       5 -   10 us |   1228 | ###                                    |
      10 -   15 us |    438 | #                                      |
      15 -   20 us |    106 |                                        |
      20 -   25 us |     21 |                                        |
      25 -   30 us |     11 |                                        |
      30 -   35 us |      1 |                                        |
      35 -   40 us |      2 |                                        |
      40 -   45 us |      4 |                                        |
      50 -   55 us |      1 |                                        |
      60 -   65 us |      1 |                                        |
      65 -   70 us |      1 |                                        |
      70 -   75 us |      1 |                                        |
      75 -   80 us |      2 |                                        |
      85 -   90 us |      1 |                                        |
      95 -  100 us |      1 |                                        |
     120 -  125 us |      1 |                                        |
     135 -  140 us |      1 |                                        |
     200 -  ... us |      2 |                                        |

Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/r/20250207080446.77630-2-gmonaco@redhat.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>

parent 4a75e8c3

tools/perf/builtin-ftrace.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -841,6 +841,7 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])

		bar_len = buckets[0] * bar_total / total;

		if (!ftrace->hide_empty \|\| buckets[0])
		printf(" %4d - %4d %s \| %10d \| %.s%s \|\n",
		0, min_latency ?: 1, use_nsec ? "ns" : "us",
		buckets[0], bar_len, bar, bar_total - bar_len, "");
		@@ -849,6 +850,8 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
		unsigned int start, stop;
		const char *unit = use_nsec ? "ns" : "us";

		if (ftrace->hide_empty && !buckets[i])
		continue;
		if (!ftrace->bucket_range) {
		start = (1 << (i - 1));
		stop = 1 << i;
		@@ -884,6 +887,8 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
		}

		bar_len = buckets[bucket_num - 1] * bar_total / total;
		if (ftrace->hide_empty && !buckets[bucket_num - 1])
		goto print_stats;
		if (!ftrace->bucket_range) {
		printf(" %4d - %-4s %s", 1, "...", use_nsec ? "ms" : "s ");
		} else {
		@@ -902,6 +907,7 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
		printf(" \| %10d \| %.s%s \|\n", buckets[bucket_num - 1],
		bar_len, bar, bar_total - bar_len, "");

		print_stats:
		printf("\n# statistics (in %s)\n", ftrace->use_nsec ? "nsec" : "usec");
		printf(" total time: %20.0f\n", latency_stats.mean * latency_stats.n);
		printf(" avg time: %20.0f\n", latency_stats.mean);
		@@ -1645,6 +1651,8 @@ int cmd_ftrace(int argc, const char **argv)
		"Minimum latency (1st bucket). Works only with --bucket-range."),
		OPT_UINTEGER(0, "max-latency", &ftrace.max_latency,
		"Maximum latency (last bucket). Works only with --bucket-range."),
		OPT_BOOLEAN(0, "hide-empty", &ftrace.hide_empty,
		"Hide empty buckets in the histogram"),
		OPT_PARENT(common_options),
		};
		const struct option profile_options[] = {

tools/perf/util/ftrace.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -25,6 +25,7 @@ struct perf_ftrace {
		unsigned int min_latency;
		unsigned int max_latency;
		unsigned int bucket_num;
		bool hide_empty;
		int graph_depth;
		int func_stack_trace;
		int func_irq_info;