Messages in this thread | | | Subject | Re: [PATCH v1 6/7] perf pmu-events: Remember the events and metrics table | From | Yang Jihong <> | Date | Sun, 8 Oct 2023 17:36:13 +0800 |
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Hello,
On 2023/10/8 13:49, Ian Rogers wrote: > On Sat, Oct 7, 2023 at 8:39 PM Yang Jihong <yangjihong1@huawei.com> wrote: >> >> Hello, >> >> On 2023/10/7 10:13, Ian Rogers wrote: >>> strcmp_cpuid_str performs regular expression comparisons. Avoid >>> repeated computation of the table by remembering the table in a >>> static. >>> >>> Signed-off-by: Ian Rogers <irogers@google.com> >>> --- >>> tools/perf/pmu-events/jevents.py | 48 +++++++++++++++++++------------- >>> 1 file changed, 28 insertions(+), 20 deletions(-) >>> >>> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py >>> index fd009752b427..8d8d5088c53c 100755 >>> --- a/tools/perf/pmu-events/jevents.py >>> +++ b/tools/perf/pmu-events/jevents.py >>> @@ -978,28 +978,32 @@ int pmu_metrics_table__for_each_metric(const struct pmu_metrics_table *table, >>> >>> const struct pmu_events_table *perf_pmu__find_events_table(struct perf_pmu *pmu) >>> { >>> - const struct pmu_events_table *table = NULL; >>> - char *cpuid = perf_pmu__getcpuid(pmu); >>> + static const struct pmu_events_table *table; >>> size_t i; >>> >>> - /* on some platforms which uses cpus map, cpuid can be NULL for >>> - * PMUs other than CORE PMUs. >>> - */ >>> - if (!cpuid) >>> - return NULL; >>> - >>> - i = 0; >>> - for (;;) { >>> - const struct pmu_events_map *map = &pmu_events_map[i++]; >>> - if (!map->arch) >>> - break; >>> - >>> - if (!strcmp_cpuid_str(map->cpuid, cpuid)) { >>> - table = &map->event_table; >>> - break; >>> + if (!table) { >> If there is no matched table in pmu_events_map, >> perf_pmu__find_events_table() will enter this branch for repeated search >> each time. >> Or do we need to use another variable to indicate whether the search has >> been performed? > > Agreed, the behavior will match the existing behavior. Longer term I > want to remove this code. Do you have a scenario we should optimize > for here? >
Yes, the CPU of the environment I'm using is "AuthenticAMD-15-6B-1" (not in the pmu_events_map). As a result, the search is repeated every time. (If `perf record true` is executed once, the search is repeated for 6 times.)
This commit avoids repeated lookups to improve performance, so if it's feasible, is it best to consider improving performance in this case as well?
Thanks, Yang
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