8324828: Avoid multiple search of reserved regions during splitting

[afshin-zafari]

To reserve two consequent memory regions, developers need to reserve a large region and then split it into two sub parts. To register memory type (MEMFLAGS) mtXXX for a region another call to NMT API is needed for every sub part. Since at every NMT call a linked list of reserved regions is searched, therefore for every split operation there are three NMT calls and search in the list.
This PR adds the memory flags of the two sub regions to the split API to avoid extra search in the list.

tiers1-5 tests passed

---

Progress

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Issue

• JDK-8324828: Avoid multiple search of reserved regions during splitting (Enhancement - P4)

Reviewers

• Thomas Stuefe (@tstuefe - Reviewer)
• Johan Sjölen (@jdksjolen - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 00: Full (f2767de9)

[tstuefe]

Good. I would have named the flags "flag1" or "flag2" or "flag_rhs", "flag_lhs" or similar, but that is just nitpicking.

[openjdk]

@afshin-zafari This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8324828: Avoid multiple search of reserved regions during splitting

Reviewed-by: stuefe, jsjolen

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At the time when this comment was updated there had been 151 new commits pushed to the master branch:

• 3a00fc7: 8323698: Class use page does not include extends/implements type arguments
• f32f574: 8326575: Remove unused ContiguousSpace::set_top_for_allocations
• 09f755a: 8325857: G1 Full GC flushes mark stats cache too early
• 1799ffe: 8310351: Typo in ImmutableCollections
• d10f277: 8326006: Allow TEST_VM_FLAGLESS to set flagless mode
• 63f6a56: 8326530: Widen allowable error bound of Math.tan
• 27574b3: 8326585: COMPARE_BUILD=PATCH fails if patch -R fails
• c26c583: 8311003: missing @SInCE info in jdk.security.jgss
• 09a78b5: 8326378: [PPC64] CodeEntryAlignment too large
• ef2d5c4: 8326065: Merge Space into ContiguousSpace
• ... and 141 more: https://git.openjdk.org/jdk/compare/c266800a3a7dd44416b0b4df3bdd78410241d74b...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[jdksjolen]

Nice!

[afshin-zafari]

Thank you @tstuefe and @jdksjolen for your reviews.
/integrate

[openjdk]

Going to push as commit 7583419.
Since your change was applied there have been 172 commits pushed to the master branch:

• c5f1dcc: 8325082: Rename headers named 'heapRegion*' of G1
• 4d82ea1: 8325144: C1: Optimize CriticalEdgeFinder
• a48f596: 8322179: RISC-V: Implement SHA-1 intrinsic
• 5daf63b: 8326636: Problem list StartupOutput.java due to 8326615
• 97aca09: 8326717: Disable stringop-overflow in shenandoahLock.cpp
• ec9437d: 8325247: Memory leak in SessionKeyRef class def when using PKCS11 security provider
• 0901ded: 8326433: Make file-local functions static in src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c
• d22d890: 8325898: ChoiceFormat returns erroneous result when formatting bad pattern
• 93feda3: 8322962: Upcall stub might go undetected when freezing frames
• fc67c2b: 8325530: Vague error message when com.sun.tools.attach.VirtualMachine fails to load agent library
• ... and 162 more: https://git.openjdk.org/jdk/compare/c266800a3a7dd44416b0b4df3bdd78410241d74b...master

Your commit was automatically rebased without conflicts.

[openjdk]

@afshin-zafari Pushed as commit 7583419.

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