RFR: JDK-8256287: [windows] add loop fuse to map_or_reserve_memory_aligned [v3]

[Yumin Qi]

On Mon, 16 Nov 2020 14:57:15 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Hi,
>> 
>> may I please have reviews for this little fix:
>> 
>> On windows, `map_or_reserve_memory_aligned()` attempts to allocate aligned memory by:
>> 1) reserving larger area
>> 2) releasing it
>> 3) attempting to re-reserve into the vacated address space a smaller area at the aligned start address
>> 
>> Since this may fail (between (2) and (3) someone may have grabbed part of that address space concurrently), we do this in a loop. However, when failing to release it we will loop-reserve endlessly.
>> 
>> This is one of the reasons for JDK-8255954 whose root cause will be fixed with JDK-8255978. But we should guard against endless loops independently from that.
>> 
>> This patch:
>> - limits the number we try this to 20. If in 20 cases someone else grabs address space concurrently, something is off...
>> - now correctly handles the return code of the release operation (1): in debug we assert, since if release_memory() fails something is wrong and we should take a look. In the release case, we now return an error.
>> 
>> 
>> Thanks!
>
> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
> 
>   feedback luhenry

LGTM

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Marked as reviewed by minqi (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1191