JDK-8281015: Further simplify NMT backend

[tstuefe]

NMT backend can be further simplified and cleaned out.

• some entry points require NMT_TrackingLevel as arguments, some use the global tracking level. Ultimately, every part of NMT always uses the global tracking level, so in many cases the explicit parameter can be removed and the global tracking level can be used instead.
• MemTracker::malloc_header_size(level) + MemTracker::malloc_footer_size(level) are fused into MemTracker::overhead_per_malloc()
• when adding to MallocSiteTable, caller gets back a shortcut to the entry. That shortcut is stored verbatim in the malloc header. It consists of two 16-bit values (bucket index and chain position). That tupel finds its way into many argument lists. It can be simplified into single 32-bit opaque marker. Code outside the MallocSiteTable does not need to know what it is.
• Currently, the MallocHeader class contains a lot of logic. It accounts (in constructor) and de-accounts (in MallocHeader::release()). It would simplify code if MallocHeader were just a dumb data carrier and the MallocTracker would do the actual work.
• MallocHeader can be simplified, almost all members made constant and modifying accessors removed.
• In some places we handle inputptr=NULL gracefully where we should assert instead
• Expressions like MemTracker::tracking_level() != NMT_off can be simplified to MemTracker::enabled().
• MemTracker::malloc_base (all variants) can be removed. Note that we have MallocTracker::malloc_header, which achieves the same and does not require casting to the header.

Testing:

• GHAs
• manually ran NMT gtests (all NMT modes) and NMT jtreg tests on Ubuntu x64
• SAP nightlies ran through. Note that since 8275301 "Unify C-heap buffer overrun checks into NMT" NMT is enabled by default in debug builds, so it gets a lot more workout in tests now.

Note that I wanted to manually verify that the gdb "call pp" command still works in order to not break Zhengyu's recent addition, but found its already broken. I filed https://bugs.openjdk.java.net/browse/JDK-8281023 and am preparing a separate patch.

---

Progress

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Issue

• JDK-8281015: Further simplify NMT backend

Reviewers

• Zhengyu Gu (@zhengyu123 - Reviewer) ⚠️ Review applies to 10e1507
• Matthias Baesken (@MBaesken - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back stuefe! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@tstuefe The following label will be automatically applied to this pull request:

• hotspot

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[mlbridge]

Webrevs

• 01: Full (f4474fc7)
• 00: Full (10e15072)

[tstuefe]

Tested at SAP for 14 days, no problems.

Any opinions? Should I reduce this patch, or split it into parts to make it more palatable?

[zhengyu123]

Overall is good, a few minor comments.

[zhengyu123]

Wanna add assert memblock != NULL?

[zhengyu123]

make mst_marker a struct? instead of opaque type.

[tstuefe]

I played around a lot with different forms (struct, union) and in the end settled on an opaque uint32 since

• it would be passed by value and I would have to provide that structure in all kind places, I got include circularities
• I have a vague improvement in my head where we store the malloc site table entries not as individually malloced elements but in a (dynamically growing) array; that would mean we could address them by index without having to walk the bucket chains; and that index would be a simple number.

[openjdk]

@tstuefe this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout nmt-cleanups
git fetch https://git.openjdk.java.net/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[tstuefe]

Thanks a lot, @zhengyu123, for your review. Sorry for the delay, I had vacation. I'll implement all your proposals excluding the last one (mst_marker as structure); see comment there.

[openjdk]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8281015: Further simplify NMT backend

Reviewed-by: zgu, mbaesken

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 7 new commits pushed to the master branch:

• 340a35d: 8282279: Interpret case-insensitive string locale independently
• 5035bf5: 8282208: Reduce MachNode size
• aaab2cb: 8282225: GHA: Allow one concurrent run per PR only
• d017e98: 8255577: Possible issues with SR_initialize
• 9332071: 8282194: C1: Missing side effects of dynamic constant linkage
• ecd85e6: 8282231: x86-32: runtime call to SharedRuntime::ldiv corrupts registers
• 378fa50: 8281962: Avoid unnecessary native calls in InflaterInputStream

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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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[MBaesken]

please check copyright years, e.g. src/hotspot/share/services/memTracker.cpp (still 2021).
Otherwise looks okay to me.

[tstuefe]

please check copyright years, e.g. src/hotspot/share/services/memTracker.cpp (still 2021). Otherwise looks okay to me.

Thank you @MBaesken !

I will fix copyrights before pushing.

[tstuefe]

/integrate

[openjdk]

Going to push as commit b96b743.
Since your change was applied there have been 32 commits pushed to the master branch:

• 9471f24: 8280684: JfrRecorderService failes with guarantee(num_written > 0) when no space left on device.
• 3efd6aa: 8282347: AARCH64: Untaken branch in has_negatives stub
• cd36be4: 8206187: javax/management/remote/mandatory/connection/DefaultAgentFilterTest.java fails with Port already in use
• bf19fc6: 8280357: user.home = "?" when running with systemd DynamicUser=true
• b6843a1: 8005885: enhance PrintCodeCache to print more data
• 23995f8: 8281525: Enable Zc:strictStrings flag in Visual Studio build
• 20e78f7: 8282307: Parallel: Incorrect discovery mode in PCReferenceProcessor
• 0b6862e: 8282348: Remove unused CardTable::dirty_card_iterate
• 6fab8a2: 8277204: Implement PAC-RET branch protection on Linux/AArch64
• abc0ce1: 8282316: Operation before String case conversion
• ... and 22 more: https://git.openjdk.java.net/jdk/compare/e1060bee2adb9f2e07ca09309d0f89132db30f28...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tstuefe Pushed as commit b96b743.

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