perf ftrace: Check min/max latency only with bucket range

It's an optional feature and remains 0 when bucket range is not given.
And it makes the histogram goes to the last entry always because any
latency (num) is greater than or equal to 0.

Before:

  $ sudo ./perf ftrace latency -a -T do_futex sleep 1
  #   DURATION     |      COUNT | GRAPH                                          |
       0 -    0 us |          0 |                                                |
       1 -    2 us |          0 |                                                |
       2 -    4 us |          0 |                                                |
       4 -    8 us |          0 |                                                |
       8 -   16 us |          0 |                                                |
      16 -   32 us |          0 |                                                |
      32 -   64 us |          0 |                                                |
      64 -  128 us |          0 |                                                |
     128 -  256 us |          0 |                                                |
     256 -  512 us |          0 |                                                |
     512 - 1024 us |          0 |                                                |
       1 -    2 ms |          0 |                                                |
       2 -    4 ms |          0 |                                                |
       4 -    8 ms |          0 |                                                |
       8 -   16 ms |          0 |                                                |
      16 -   32 ms |          0 |                                                |
      32 -   64 ms |          0 |                                                |
      64 -  128 ms |          0 |                                                |
     128 -  256 ms |          0 |                                                |
     256 -  512 ms |          0 |                                                |
     512 - 1024 ms |          0 |                                                |
       1 - ...  s  |       1353 | ############################################## |

After:

  $ sudo ./perf ftrace latency -a -T do_futex sleep 1
  #   DURATION     |      COUNT | GRAPH                                          |
       0 -    0 us |        321 | ###########                                    |
       1 -    2 us |        132 | ####                                           |
       2 -    4 us |        202 | #######                                        |
       4 -    8 us |        188 | ######                                         |
       8 -   16 us |         16 |                                                |
      16 -   32 us |         12 |                                                |
      32 -   64 us |         30 | #                                              |
      64 -  128 us |         98 | ###                                            |
     128 -  256 us |         53 | #                                              |
     256 -  512 us |         57 | ##                                             |
     512 - 1024 us |          9 |                                                |
       1 -    2 ms |          9 |                                                |
       2 -    4 ms |          1 |                                                |
       4 -    8 ms |         98 | ###                                            |
       8 -   16 ms |          5 |                                                |
      16 -   32 ms |          7 |                                                |
      32 -   64 ms |         32 | #                                              |
      64 -  128 ms |         10 |                                                |
     128 -  256 ms |         10 |                                                |
     256 -  512 ms |          2 |                                                |
     512 - 1024 ms |          0 |                                                |
       1 - ...  s  |          0 |                                                |

Fixes: 690a052a6d85c530 ("perf ftrace latency: Add --max-latency option")
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Gabriele Monaco <gmonaco@redhat.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250108210015.1188531-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 08c1cc429b27e169c8adc95ba09e463c62bd2829..90cf2c9915a7e35b603f5ec56990575ca2d13dc8 100644 (file)
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -796,8 +796,10 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
                        // than the min latency desired.
                        if (num > 0) // 1st entry: [ 1 unit .. bucket_range units ]
                                i = num / ftrace->bucket_range + 1;
+                       if (num >= max_latency - min_latency)
+                               i = NUM_BUCKET -1;
                }
-               if (i >= NUM_BUCKET || num >= max_latency - min_latency)
+               if (i >= NUM_BUCKET)
                        i = NUM_BUCKET - 1;
 
                num += min_latency;
@@ -1738,7 +1740,7 @@ int cmd_ftrace(int argc, const char **argv)
                        ret = -EINVAL;
                        goto out_delete_filters;
                }
-               if (!ftrace.min_latency) {
+               if (ftrace.bucket_range && !ftrace.min_latency) {
                        /* default min latency should be the bucket range */
                        ftrace.min_latency = ftrace.bucket_range;
                }
@@ -1749,7 +1751,7 @@ int cmd_ftrace(int argc, const char **argv)
                        ret = -EINVAL;
                        goto out_delete_filters;
                }
-               if (!ftrace.max_latency) {
+               if (ftrace.bucket_range && !ftrace.max_latency) {
                        /* default max latency should depend on bucket range and num_buckets */
                        ftrace.max_latency = (NUM_BUCKET - 2) * ftrace.bucket_range +
                                                ftrace.min_latency;