Bug ID: JDK-8318636 Add jcmd to print annotated process memory map

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JDK 21	JDK 22
21.0.8Fixed	22 b24Fixed

Analysts and supporters often use /proc/xx/maps to make sense of the memory footprint of a process.

Interpreting the memory map correctly can help when used as a complement to other tools (e.g. NMT). There even exist tools out there that attempt to annotate the process memory map with JVM information.

That, however, can be much more easily and accurately done within the JVM. At least for mappings originating from hotspots, we have the relevant information in NMT.

[jdk21u-fix-request] Approval Request from Andreas Steiner We want to have this very helpful supportability feature in jdk21u-dev too. Risk is low because new code is only executed if the new jcmd is used. Patch is mostly clean apart from code movement and some test changes. Follow up changes planed: https://bugs.openjdk.org/browse/JDK-8326586, https://bugs.openjdk.org/browse/JDK-8322475 + https://bugs.openjdk.org/browse/JDK-8335710
27-02-2025
Agreed. But I think we should defer this one to the July 2025 release (it's already late in the April cycle).
24-02-2025
[~sgehwolf] This would be useful to have in 21. Risk is low, Patch is mostly clean apart from code movement and some test changes.
21-02-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk21u-dev/pull/1415 Date: 2025-02-19 13:25:34 +0000
19-02-2025
[~stuefe] Thomas - can a release note be created for this enhancement ?
04-02-2025
[~stuefe] Could a release note be created for this new functionality ? Thanks. https://openjdk.org/guide/#release-notes
09-01-2025
The dumped process map file is not large , for example : ls -alL pmap.txt -rw-r--r-- 1 xxxx yyyyy 18223 Mar 19 16:52 pmap.txt Why don't we output it in failure case in the test ? Would help to analyze the issue. ( Btw. System.dump_map could be any kind of map, it is not a very helpful/descriptive name. Why not System.dump_pmem_map (still rather short) or something similar? )
19-03-2024
Since March we saw a couple of failures (on linuxx86_64 / linuxaarch64) in our nightlies in the test serviceability/dcmd/vm/SystemDumpMapTest.java. (no issues before) The failure log output looks like : Missing patterns in dump: .0x\\p{XDigit}+ - 0x\\p{XDigit}+ +\\d+.META.* .0x\\p{XDigit}+ - 0x\\p{XDigit}+ +\\d+.JAVAHEAP.* .0x\\p{XDigit}+ - 0x\\p{XDigit}+ +\\d+.STACK.main. .0x\\p{XDigit}+ - 0x\\p{XDigit}+ +\\d+.CODE.* test SystemDumpMapTest.jmx(): failure java.lang.RuntimeException: java.lang.RuntimeException: Missing patterns might be interesting to check/output a bit more in failure cases (is the vm_memory_map_<pid>.txt maybe empty? Or ends before the expected things ?).
19-03-2024
Changeset: 6f863b2a Author: Thomas Stuefe <stuefe@openjdk.org> Date: 2023-11-13 08:26:42 +0000 URL: https://git.openjdk.org/jdk/commit/6f863b2a1baa67deb2a7b33fcd93d272aea01812
13-11-2023
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/16301 Date: 2023-10-22 10:08:49 +0000
22-10-2023

Relates :	JDK-8319948 - jcmd man page needs to be updated
Relates :	JDK-8322811 - jcmd System.dump_map help info has conflicting statements
Relates :	JDK-8319873 - Add windows implementation for jcmd System.map and System.dump_map
Relates :	JDK-8334026 - Provide a diagnostic PrintMemoryMapAtExit switch on Linux
Relates :	JDK-8322475 - Extend printing for System.map
Relates :	JDK-8326586 - Improve Speed of System.map
Relates :	JDK-8319875 - Add macOS implementation for jcmd System.map