RFR: 8278396: G1: Initialize the BOT threshold to be region bottom

[Albert Mingkun Yang]

On Tue, 21 Dec 2021 12:05:38 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> This simple patch tightens the assert for offset card value and drops the special treatment of the first card for a region.
>> 
>> Test: tier1-5
>
> src/hotspot/share/gc/g1/heapRegion.cpp line 801:
> 
>> 799: 
>> 800: void HeapRegion::initialize_bot_threshold() {
>> 801:   _bot_part.reset_bot();
> 
> As a follow-up it might be nice to also rename the function here and update the usage to have matching naming for parameters and such.

Maybe sth similar to https://bugs.openjdk.java.net/browse/JDK-8279008 can be done for `G1BlockOffsetTablePart::_next_offset_threshold` as well. Then, there's no need to (re)init the threshold.

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PR: https://git.openjdk.java.net/jdk/pull/6762