rtla/timerlat: Fix histogram report when a cpu count is 0

JIRA: https://issues.redhat.com/browse/RHEL-50869

commit 01b05fc
Author: John Kacur <jkacur@redhat.com>
Date:   Fri May 10 15:03:18 2024 -0400

    rtla/timerlat: Fix histogram report when a cpu count is 0

    On short runs it is possible to get no samples on a cpu, like this:

      # rtla timerlat hist -u -T50

      Index   IRQ-001   Thr-001   Usr-001   IRQ-002   Thr-002   Usr-002
      2             1         0         0         0         0         0
      33            0         1         0         0         0         0
      36            0         0         1         0         0         0
      49            0         0         0         1         0         0
      52            0         0         0         0         1         0
      over:         0         0         0         0         0         0
      count:        1         1         1         1         1         0
      min:          2        33        36        49        52 18446744073709551615
      avg:          2        33        36        49        52         -
      max:          2        33        36        49        52         0
      rtla timerlat hit stop tracing
        IRQ handler delay:          (exit from idle)            48.21 us (91.09 %)
        IRQ latency:                                                    49.11 us
        Timerlat IRQ duration:                                   2.17 us (4.09 %)
        Blocking thread:                                         1.01 us (1.90 %)
                           swapper/2:0                           1.01 us
      ------------------------------------------------------------------------
        Thread latency:                                         52.93 us (100%)

      Max timerlat IRQ latency from idle: 49.11 us in cpu 2

    Note, the value 18446744073709551615 is the same as ~0.

    Fix this by reporting no results for the min, avg and max if the count
    is 0.

    Link: https://lkml.kernel.org/r/20240510190318.44295-1-jkacur@redhat.com

    Cc: stable@vger.kernel.org
    Fixes: 1eeb632 ("rtla/timerlat: Add timerlat hist mode")
    Suggested-by: Daniel Bristot de Oliveria <bristot@kernel.org>
    Signed-off-by: John Kacur <jkacur@redhat.com>
    Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>

Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>

Author: lclaudio

tools/tracing/rtla/src/timerlat_hist.c

@@ -325,17 +325,29 @@ timerlat_print_summary(struct timerlat_hist_params *params,
 		if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
 			continue;
 
-		if (!params->no_irq)
-			trace_seq_printf(trace->seq, "%9llu ",
-					data->hist[cpu].min_irq);
+		if (!params->no_irq) {
+			if (data->hist[cpu].irq_count)
+				trace_seq_printf(trace->seq, "%9llu ",
+						data->hist[cpu].min_irq);
+			else
+				trace_seq_printf(trace->seq, "        - ");
+		}
 
-		if (!params->no_thread)
-			trace_seq_printf(trace->seq, "%9llu ",
-					data->hist[cpu].min_thread);
+		if (!params->no_thread) {
+			if (data->hist[cpu].thread_count)
+				trace_seq_printf(trace->seq, "%9llu ",
+						data->hist[cpu].min_thread);
+			else
+				trace_seq_printf(trace->seq, "        - ");
+		}
 
-		if (params->user_hist)
-			trace_seq_printf(trace->seq, "%9llu ",
-					data->hist[cpu].min_user);
+		if (params->user_hist) {
+			if (data->hist[cpu].user_count)
+				trace_seq_printf(trace->seq, "%9llu ",
+						data->hist[cpu].min_user);
+			else
+				trace_seq_printf(trace->seq, "        - ");
+		}
 	}
 	trace_seq_printf(trace->seq, "\n");
 
@@ -385,17 +397,29 @@ timerlat_print_summary(struct timerlat_hist_params *params,
 		if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
 			continue;
 
-		if (!params->no_irq)
-			trace_seq_printf(trace->seq, "%9llu ",
-					data->hist[cpu].max_irq);
+		if (!params->no_irq) {
+			if (data->hist[cpu].irq_count)
+				trace_seq_printf(trace->seq, "%9llu ",
+						 data->hist[cpu].max_irq);
+			else
+				trace_seq_printf(trace->seq, "        - ");
+		}
 
-		if (!params->no_thread)
-			trace_seq_printf(trace->seq, "%9llu ",
-					data->hist[cpu].max_thread);
+		if (!params->no_thread) {
+			if (data->hist[cpu].thread_count)
+				trace_seq_printf(trace->seq, "%9llu ",
+						data->hist[cpu].max_thread);
+			else
+				trace_seq_printf(trace->seq, "        - ");
+		}
 
-		if (params->user_hist)
-			trace_seq_printf(trace->seq, "%9llu ",
-					data->hist[cpu].max_user);
+		if (params->user_hist) {
+			if (data->hist[cpu].user_count)
+				trace_seq_printf(trace->seq, "%9llu ",
+						data->hist[cpu].max_user);
+			else
+				trace_seq_printf(trace->seq, "        - ");
+		}
 	}
 	trace_seq_printf(trace->seq, "\n");
 	trace_seq_do_printf(trace->seq);