RFR: 8271195: Use largest available large page size smaller than LargePageSizeInBytes when available [v3]

[Jatin Bhateja]

On Fri, 4 Feb 2022 15:47:52 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> I believe it was https://bugs.openjdk.java.net/browse/JDK-8007074. Wasn't that the reason that large page memory on Linux gets committed right away when reserving?
>
> Yes, it was.

MAP_FIXED semantics are clear here, any existing reserved mapping will get overridden if a new commit happens over it, but only if new commit happens over the existing reserved address space, reservation takes a NULL address argument and returns the block of virtual memory which can be committed by binding it to large pages, since we are not bookkeeping the reserved memory space for any subsequent commit hence won't any unreserved virtual memory from a previous commit failure cause a leak in the virtual address space.

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PR: https://git.openjdk.java.net/jdk/pull/7326