On Tue, 19 Aug 2025 14:27:59 GMT, Jonas Norlinder <[email protected]> wrote:
> now we finally have a specific method that is called for GC activites...
Then, it should be in `Universe::before_exit`, not inside heap.
>> src/hotspot/share/services/cpuTimeUsage.hpp line 47:
>>
>>> 45: static jlong gc_threads();
>>> 46: static jlong vm_thread();
>>> 47: static jlong stringdedup();
>>
>> I feel the API surface contains some redundancy.
>>
>> For example, the GC-part API design exposes two ways to query and they are
>> essentially the same -- for the sake of simplicity, I'd suggest keeping only
>> one.
>>
>> The calculation of `total` should be done by users of this API, I believe,
>> when/if total is desirable.
>
> The motivation for `total()` is that this is probably what most users want,
> but in case anyone want a sub-component I also expose each one of them. It
> also serves as documentation as what we currently consider to be "total", so
> I would prefer keeping it.
>
> If you look at e.g. `WeakProcessor::CountingClosure` the following is defined
>
> size_t dead() const { return _old_dead + _new_dead; }
> size_t new_dead() const { return _new_dead; }
> size_t total() const { return dead() + _live; }
>
>
> so having such convenience method in hotspot is not unprecedented and I would
> prefer keeping it.
>
> `statistics()` is a less important convenience method that can be removed.
I think the smallest API would be `statisics()`, which returns all
sub-components, and consumers of this API can calculate other derived metrics.
YMMV.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/26621#discussion_r2285544932
PR Review Comment: https://git.openjdk.org/jdk/pull/26621#discussion_r2285551132
