RFR: 8322043: HeapDumper should use parallel dump by default [v3]

[Alex Menkov]

On Tue, 16 Apr 2024 09:08:20 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   check free_memory for OOME
>
> src/hotspot/share/services/heapDumper.hpp line 63:
> 
>> 61:   // additional info is written to out if not null.
>> 62:   // compression >= 0 creates a gzipped file with the given compression level.
>> 63:   // parallel_thread_num >= 0 indicates thread numbers of parallel object dump, -1 means "auto select".
> 
> I don't understand why you need to add `-1` to mean "auto-select" instead of just setting the default parameter to be `default_num_of_dump_threads()`?

I think it makes the code more flexible - it allows to distinguish between "use default value" and "I don't care" cases.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18748#discussion_r1567864860