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lenticularis39rostedt
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rtla/timerlat: Make timerlat_top_cpu->*_count unsigned long long
Most fields of struct timerlat_top_cpu are unsigned long long, but the fields {irq,thread,user}_count are int (32-bit signed). This leads to overflow when tracing on a large number of CPUs for a long enough time: $ rtla timerlat top -a20 -c 1-127 -d 12h ... 0 12:00:00 | IRQ Timer Latency (us) | Thread Timer Latency (us) CPU COUNT | cur min avg max | cur min avg max 1 #43200096 | 0 0 1 2 | 3 2 6 12 ... 127 #43200096 | 0 0 1 2 | 3 2 5 11 ALL #119144 e4 | 0 5 4 | 2 28 16 The average latency should be 0-1 for IRQ and 5-6 for thread, but is reported as 5 and 28, about 4 to 5 times more, due to the count overflowing when summed over all CPUs: 43200096 * 127 = 5486412192, however, 1191444898 (= 5486412192 mod MAX_INT) is reported instead, as seen on the last line of the output, and the averages are thus ~4.6 times higher than they should be (5486412192 / 1191444898 = ~4.6). Fix the issue by changing {irq,thread,user}_count fields to unsigned long long, similarly to other fields in struct timerlat_top_cpu and to the count variable in timerlat_top_print_sum. Link: https://lore.kernel.org/[email protected] Reported-by: Attila Fazekas <[email protected]> Signed-off-by: Tomas Glozar <[email protected]> Signed-off-by: Steven Rostedt (Google) <[email protected]>
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tools/tracing/rtla/src/timerlat_top.c

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -54,9 +54,9 @@ struct timerlat_top_params {
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};
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struct timerlat_top_cpu {
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int irq_count;
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int thread_count;
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int user_count;
57+
unsigned long long irq_count;
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unsigned long long thread_count;
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unsigned long long user_count;
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unsigned long long cur_irq;
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unsigned long long min_irq;
@@ -280,7 +280,7 @@ static void timerlat_top_print(struct osnoise_tool *top, int cpu)
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/*
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* Unless trace is being lost, IRQ counter is always the max.
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*/
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trace_seq_printf(s, "%3d #%-9d |", cpu, cpu_data->irq_count);
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trace_seq_printf(s, "%3d #%-9llu |", cpu, cpu_data->irq_count);
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if (!cpu_data->irq_count) {
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trace_seq_printf(s, "%s %s %s %s |", no_value, no_value, no_value, no_value);

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