On Fri, 1 Dec 2023 09:58:16 GMT, Stefan Johansson <sjoha...@openjdk.org> wrote:
>> I thought it is typically preferred to initialize a singleton object on the >> heap, rather than using several static variables. It is easier to control >> the initialization order and timing of an on-heap singleton object than >> statics. >> >> Moreover, for this class, `initialize()` could also check `if >> (UsePerfData)`, and only create the singleton object under `UsePerfData`. >> This could save some memory when `UsePerfData` is false. > > I would say it depends on the use-case and here when switching to use static > functions to use the instance it felt more like an all-static class. I agree > that it would be nice to avoid the additional memory usage if `UsePerfData` > is `false` so I'm ok with keeping the instance if we add that. > It is easier to control the initialization order and timing of an on-heap > singleton object than statics. It's generally true, but the init of CPUTimeCounters is not sensitive to ordering. > This could save some memory when UsePerfData is false. True, but the mem savings will be marginal at most, `PerfCounter* _cpu_time_counters[static_cast<int>(CPUTimeGroups::CPUTimeType::COUNT)];` will be 8 * ~12 = ~96 bytes (including future cpu-time-type enums). (I don't have a strong preference here; however, I'd like to make the pros and cons explicit.) ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/15082#discussion_r1412193296
