RFR: JDK-8304820: Statically allocate ObjectSynchronizer mutexes [v3]

[Justin King]

On Tue, 28 Mar 2023 11:40:42 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> src/hotspot/share/runtime/synchronizer.cpp line 255:
>> 
>>> 253: // by property of the storage itself being aligned to that requirement and each entry storage being
>>> 254: // `sizeof(PlatformMutex)` aligned up to `alignof(PlatformMutex)`.
>>> 255: alignas(PlatformMutex) static uint8_t _inflation_locks[inflation_lock_count()][align_up(sizeof(PlatformMutex), alignof(PlatformMutex))];
>> 
>> I'm afraid you lost me here. Why does this have to be so convoluted/obscure?
>
> I thought `sizeof(T)` always was a multiple of `alignof(T)`. Is there some case where this is not true?

Ah, I had assumed it wasn't required. But a quick glance says it is. So I'll remove the `align_up`. Should be more simple now.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13160#discussion_r1150606641