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

[Stefan Johansson]

On Fri, 4 Feb 2022 12:20:17 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>>> which left holes in the virtual address space
>> 
>> That sounds like virtual address leaking; should be dealt with in its own ticket/PR.
>
> New ticket created:
> https://bugs.openjdk.java.net/browse/JDK-8281263

The documentation around `mmap` with MAP_FIXED is not crystal clear on failure. In the case we return false from `commit_memory_special(...)` the commit over the reserved range failed and I'm pretty sure that when it does the virtual memory range reserved becomes available to the system again and might be reused by some other thread. So unmapping that range would break any such reservation. @stefank isn't this what we've had problems with in the past?

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