RFR: 8318986: Improve GenericWaitBarrier performance [v3]

[Aleksey Shipilev]

On Tue, 7 Nov 2023 08:56:09 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with four additional commits since the last revision:
>> 
>>  - Touchups
>>  - More comments work
>>  - Tight up the comments
>>  - Rework to a single atomic counter per cell
>
> src/hotspot/share/utilities/waitBarrier_generic.cpp line 151:
> 
>> 149:     _sem.signal();
>> 150: 
>> 151:     if (wakeups++ > max) {
> 
> I would assume max = 2, would call signal() max 2 times ?
> Here we end when wakeups are larger than max with post inc, so isn't that 4 times? (0->3)

Right. Should be `++wakeups >= max` to match the limit exactly. Going to fix it in next commits.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16404#discussion_r1384640849