RFR: 8326688: Parallel: Remove unnecessary BOT update in UpdateOnlyClosure::do_addr

[Thomas Schatzl]

On Thu, 29 Feb 2024 10:01:59 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> src/hotspot/share/gc/parallel/psParallelCompact.cpp line 2554:
>> 
>>> 2552: 
>>> 2553: inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
>>> 2554:   _start_array->update_for_block(addr, addr + cast_to_oop(addr)->size());
>> 
>> The change looks reasonable. Instead of the update, would it be possible to do verification in debug mode?
>
> Currently, BOT entries are verified on-update, the last statement of `update_for_block_work`. In my experience, they are rarely corrupted.

That is my suggestion: because they are not updated any more, there will be no verification. You are right that they are rarely corrupted so that the VM crashes, but if they are not optimal, hard to detect performance issues may creep in.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18008#discussion_r1508687594