8255848: -Xlog:gc+heap+exit shows "used 0K"

[kstefanj]

Please review this small change to improve the exit heap-log for G1.

Currently if all allocations fit into one region the exit log will faulty state that the usage is 0K:

$ java -Xlog:gc+heap+exit -Xshare:off -Xmx16g -version
[0.072s][info][gc,heap,exit] garbage-first heap total 1032192K, used 0K [0x00000003c0000000, 0x00000007c0000000)
[0.072s][info][gc,heap,exit] region size 8192K, 1 young (8192K), 0 survivors (0K)

This is cause by G1 using used_unlocked(), which doesn't take the current allocation region(s) into account. My proposed change is to check if the Heap_lock is taken and if so use used() instead of used_unlocked(). For the exit logging the lock will be held, but this log is printed using G1CollectedHeap::print_on() and we might want to allow calling this without requiring holding the heap lock.

---

Progress

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Testing

	Linux x64	Linux x86	Windows x64	macOS x64
Build	✔️ (5/5 passed)	✔️ (2/2 passed)	✔️ (2/2 passed)	✔️ (2/2 passed)
Test (tier1)	✔️ (9/9 passed)	✔️ (9/9 passed)	✔️ (9/9 passed)	✔️ (9/9 passed)

Issue

• JDK-8255848: -Xlog:gc+heap+exit shows "used 0K"

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer)
• Albert Mingkun Yang (@albertnetymk - Author)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/1051/head:pull/1051
$ git checkout pull/1051

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[openjdk]

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[mlbridge]

Webrevs

• 00: Full (267091f)

[tschatzl]

lgtm.

[openjdk]

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

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

8255848: -Xlog:gc+heap+exit shows "used 0K"

Reviewed-by: tschatzl, ayang

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At the time when this comment was updated there had been 27 new commits pushed to the master branch:

• 7f4d873: 8255215: Unsupported 'valign' attribute for 'tr' tag used in j.s.t.h.HTMLDocument
• 724217c: 8255893: Problemlist runtime/cds/appcds/jigsaw/NewModuleFinderTest.java
• 6023f6b: 8188055: (ref) Add Reference::refersTo predicate
• ab9192e: 8255681: print callstack in error case in runAWTLoopWithApp
• c7a2c24: 8255797: ciReplay: improve documentation of replay file syntax in parser
• a5d8a9c: 8255617: Zero: purge the remaining bytecode interpreter profiling support
• 4b88119: 8253037: G1: Improve check for string dedup
• 2668d23: 8255861: Also update jaotc.1 for JDK 16
• 76fa974: 8255850: Hotspot recompiled on first incremental build
• 622f72b: 8255853: Update all nroff manpages for JDK 16 release
• ... and 17 more: https://git.openjdk.java.net/jdk/compare/1d0bd50624e3fe1c1ecbeac5311994e1e3f42b26...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[kstefanj]

/integrate

[openjdk]

@kstefanj Since your change was applied there have been 44 commits pushed to the master branch:

• eb85b8d: 8255665: C2 should aggressively remove temporary hook nodes
• 18bc95b: 8250625: Compiler implementation of Pattern Matching for instanceof (Final)
• 60e4aca: 8255890: Zero: remove unused methods from BytecodeInterpreter
• 397bae2: 8255860: Clean up CDS logging related to lambda
• 97a81ce: 8253385: annotation processors remove varargs information from record components
• 166c728: 8255858: Add debug agent support for storing thread names
• a0ade22: 8255900: x86: Reduce impact when VerifyOops is disabled
• 29db1dc: 8255886: Shenandoah: Resolve cset address truncation and register clash in interpreter LRB
• 26e7ef7: 8252870: Finalize (remove "incubator" from) jpackage
• 804bd72: 8255128: linux x86 build failure with libJNIPoint.c
• ... and 34 more: https://git.openjdk.java.net/jdk/compare/1d0bd50624e3fe1c1ecbeac5311994e1e3f42b26...master

Your commit was automatically rebased without conflicts.

Pushed as commit 397972e.

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