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

[Thomas Stuefe]

On Fri, 4 Feb 2022 15:22:18 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> 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?
>
> Yes, that is my understanding.

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?

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