RFR: 8329223: Parallel: Parallel GC resizes heap even has -Xms = -Xmx [v7]

[Albert Mingkun Yang]

On Mon, 22 Apr 2024 13:06:39 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> src/hotspot/share/gc/shared/genArguments.cpp line 311:
>> 
>>> 309:     } else if (initial_old_size < MinOldSize) {
>>> 310:       log_warning(gc, ergo)("Inconsistency between initial old size and minimum old size");
>>> 311:       MinOldSize = initial_old_size;
>> 
>> Should this be `initial_old_size = MinOldSize;`?
>
>> Should this be `initial_old_size = MinOldSize;`?
> 
> Any reason why? 
> 
> The reason I picked current form because the original line was `MinOldSize = MIN2(initial_old_size, MinHeapSize - MinNewSize);`
> 
> Thanks

It's mostly to be consistent with `initial_old_size = MaxOldSize;` a few lines above; if the cmdline `OldSize` is inconsistent with other flags, change `OldSize` to fit others.

Technically, when there's inconsistency in cmdline flags, change any of them is equally correct, IMO. In the long run, maybe it's possible to remove the `OldSize` flag, since one can achieve old-size via `InitialHeapSize` and `NewSize`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18539#discussion_r1574746949