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Sender: John Kacur <jkacur@gmail.com>
From: John Kacur <jkacur@redhat.com>
To: Daniel Bristot de Oliveria <bristot@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	linux-trace-devel@vger.kernel.org
Cc: lkml <linux-kernel@vger.kernel.org>,
	stable@vger.kernel.org,
	John Kacur <jkacur@redhat.com>
Subject: [PATCH] Fix reporting when a cpu count is 0
Date: Fri, 10 May 2024 12:26:05 -0400
Message-ID: <20240510162605.28050-1-jkacur@redhat.com>
Precedence: bulk
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On short runs it is possible to get no samples on a cpu, like this

rtla timerlat hist -P f:95 -u -c0-11 -E3500 -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

This solution came from Daniel Bristot de Oliveria <bristot@kernel.org>

Fixes: 1eeb6328e8b3 ("rtla/timerlat: Add timerlat hist mode")
Tested-by: John Kacur <jkacur@redhat.com>
Signed-off-by: John Kacur <jkacur@redhat.com>
---
 tools/tracing/rtla/src/timerlat_hist.c | 60 ++++++++++++++++++--------
 1 file changed, 42 insertions(+), 18 deletions(-)

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 8bd51aab6513..5b869caed10d 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -324,17 +324,29 @@ 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");
 
@@ -384,17 +396,29 @@ 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);
-- 
2.44.0