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When testing metric expressions we fake counter values from 1 going upward. For some metrics this can yield negative values that are clipped to zero, and then cause divide by zero failures. Such clipping is questionable but may be a result of tools automatically generating metrics. A workaround for this case is to try a second time with counter values going in the opposite direction. This case was seen in a metric like: event1 / max(event2 - event3, 0) But it may also happen in more sensible metrics like: event1 / (event2 + event3 - 1 - event4) Reviewed-by: John Garry <john.garry@huawei.com> Signed-off-by: Ian Rogers <irogers@google.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kajol Jain <kjain@linux.ibm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: https://lore.kernel.org/r/20211223185622.3435128-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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