diff options
| author | Tomas Glozar <tglozar@redhat.com> | 2024-10-11 14:10:14 +0200 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2024-10-11 19:09:57 +0200 |
| commit | 4eba4723c5254ba8251ecb7094a5078d5c300646 (patch) | |
| tree | fcaec042b9aab1c84ded94dfd9594952f05536ad /tools/tracing | |
| parent | tools/rtla: fix collision with glibc sched_attr/sched_set_attr (diff) | |
| download | linux-4eba4723c5254ba8251ecb7094a5078d5c300646.tar.xz linux-4eba4723c5254ba8251ecb7094a5078d5c300646.zip | |
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/20241011121015.2868751-1-tglozar@redhat.com
Reported-by: Attila Fazekas <afazekas@redhat.com>
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'tools/tracing')
| -rw-r--r-- | tools/tracing/rtla/src/timerlat_top.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c index 94a2f5bbaeb7..7fb85c8ee3bc 100644 --- a/tools/tracing/rtla/src/timerlat_top.c +++ b/tools/tracing/rtla/src/timerlat_top.c @@ -54,9 +54,9 @@ struct timerlat_top_params { }; struct timerlat_top_cpu { - int irq_count; - int thread_count; - int user_count; + unsigned long long irq_count; + unsigned long long thread_count; + unsigned long long user_count; unsigned long long cur_irq; unsigned long long min_irq; @@ -280,7 +280,7 @@ static void timerlat_top_print(struct osnoise_tool *top, int cpu) /* * Unless trace is being lost, IRQ counter is always the max. */ - trace_seq_printf(s, "%3d #%-9d |", cpu, cpu_data->irq_count); + trace_seq_printf(s, "%3d #%-9llu |", cpu, cpu_data->irq_count); if (!cpu_data->irq_count) { trace_seq_printf(s, "%s %s %s %s |", no_value, no_value, no_value, no_value); |