[jdk21] Integrated: 8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found

[Axel Boldt-Christmas]

On Mon, 3 Jul 2023 14:24:05 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> Backport of JDK-8310743
> 
>> JDK-8309675 tried to solve the issue of NMT reporting to much committed memory by faking the virtual addresses registered when committing physical memory. This mapping was simply the virtual address  = physical offset in backing file + heap base. This works when ZGC gets a contiguous heap which starts at the heap base. However fails if it does not start at the heap base or is discontiguous.
>>
>>This proposal fixes this by keeping track of all the reserved virtual address ranges and by creating a mapping from the physical offsets to the actual reserved virtual address ranges. If the physical offsets committed maps to multiple reserved ranges, it is processed as multiple commits.
>>
>>The develop flag ZForceDiscontiguousHeapReservations is introduced to test the discontiguous heap feature and interactions.
> 
> This pull request contains a backport of commit [f393975](https://github.com/openjdk/jdk/commit/f393975d1b9423835a7aa42f6ffc0656499701d7) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.
> With merge conflict in `src/hotspot/share/gc/z/zPhysicalMemory.cpp` (header includes) resolved.

This pull request has now been integrated.

Changeset: c9111d57
Author:    Axel Boldt-Christmas <aboldtch at openjdk.org>
URL:       https://git.openjdk.org/jdk21/commit/c9111d57ce132d70d4360535254658ef6b8d134d
Stats:     477 lines in 12 files changed: 429 ins; 32 del; 16 mod

8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found

Reviewed-by: ayang
Backport-of: f393975d1b9423835a7aa42f6ffc0656499701d7

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PR: https://git.openjdk.org/jdk21/pull/92