8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux #19660

tstuefe · 2024-06-11T14:01:27Z

To investigate footprint problems of processes with a short lifespan (e.g. startup footprint problems), we found it very useful to be able to get an annotated memory map at exit - the same map printed by jcmd System.map.

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Issue

JDK-8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux (Enhancement - P4)

Reviewers

David Holmes (@dholmes-ora - Reviewer)
Matthias Baesken (@MBaesken - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/19660/head:pull/19660
$ git checkout pull/19660

Update a local copy of the PR:
$ git checkout pull/19660
$ git pull https://git.openjdk.org/jdk.git pull/19660/head

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Checkout this PR locally:
$ git pr checkout 19660

View PR using the GUI difftool:
$ git pr show -t 19660

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Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/19660.diff

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bridgekeeper · 2024-06-11T14:02:12Z

👋 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 · 2024-06-11T14:02:47Z

@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:

8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux

Reviewed-by: dholmes, 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 91 new commits pushed to the master branch:

d7dad50: 8334544: C2: wrong control assigned in PhaseIdealLoop::clone_assertion_predicate_for_unswitched_loops()
ff30240: 8334239: Introduce macro for ubsan method/function exclusions
2d4185f: 8332717: ZGC: Division by zero in heuristics
fad6644: 8333754: Add a Test against ECDSA and ECDH NIST Test vector
b211929: 8334570: Problem list gc/TestAlwaysPreTouchBehavior.java
4e58d8c: 8309821: Link to hidden classes section in Class specification for Class::isHidden
78682fe: 8329288: Update Visual Studio visibility support for POSIX functions
bcf4bb4: 8333344: JMX attaching of Subject does not work when security manager not allowed
856931d: 8304732: jdk/jfr/api/consumer/recordingstream/TestStop.java failed again with "Expected outer stream to have 3 events"
01ee424: 8294960: Convert java.base/java.lang.invoke package to use the Classfile API to generate lambdas and method handles
... and 81 more: https://git.openjdk.org/jdk/compare/aaaa86b57172d45d1126c50efc270c6e49aba7a5...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.

openjdk · 2024-06-11T14:03:17Z

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

hotspot-runtime

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2024-06-12T07:13:43Z

Webrevs

01: Full - Incremental (f03983b3)
00: Full (2b3a3f98)

dholmes-ora

Seems quite reasonable. One query and a couple of minor nits.

Thanks

dholmes-ora · 2024-06-14T04:38:35Z

test/hotspot/jtreg/runtime/NMT/PrintMemoryMapAtExitTest.java

+        ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
+      "-XX:+UnlockDiagnosticVMOptions", "-XX:+PrintMemoryMapAtExit",
+                "-XX:NativeMemoryTracking=summary", "-version");


Nit: indentation is off here.

dholmes-ora · 2024-06-14T04:40:01Z

test/hotspot/jtreg/runtime/NMT/PrintMemoryMapAtExitTest.java

+        output.shouldContain("Memory mappings");
+        output.shouldContain("JAVAHEAP");
+        output.shouldHaveExitValue(0);


Suggestion: check the exit value first. If we crashed then the other checks will likely fail before we get here.

dholmes-ora · 2024-06-14T04:45:01Z

src/hotspot/share/nmt/memMapPrinter.cpp

@@ -203,6 +204,8 @@ static void print_thread_details(uintx thread_id, const char* name, outputStream
 // Given a region [from, to), if it intersects a known thread stack, print detail infos about that thread.
 static void print_thread_details_for_supposed_stack_address(const void* from, const void* to, outputStream* st) {

+  ResourceMark rm;


Why was this needed to be added here? Shouldn't callers have any needed ResourceMarks?

It is needed because in this function we call Thread::name() which for java threads returns an RA-allocated string. This issue popped up now because we are called without a ResourceMark at VM exit. I have not investigated closer since I think the Resourcemark makes sense here: The function does not export any RA-allocated memory but may be called in a loop many times.

Okay. I was trying to find where the existing callers have their RM and it is not obvious.

Existing caller is DCmd::parse_and_execute, where we have an RM that guards every individual Dcmd execution. So, this had been a small leak of sorts, since we accumulate thread names for all java threads printed.

tstuefe · 2024-06-18T08:35:41Z

Thanks @dholmes-ora !

I worked in your remarks.

dholmes-ora

Looks good. Thanks

dholmes-ora · 2024-06-18T09:23:43Z

src/hotspot/share/nmt/memMapPrinter.cpp

@@ -203,6 +204,8 @@ static void print_thread_details(uintx thread_id, const char* name, outputStream
 // Given a region [from, to), if it intersects a known thread stack, print detail infos about that thread.
 static void print_thread_details_for_supposed_stack_address(const void* from, const void* to, outputStream* st) {

+  ResourceMark rm;


Okay. I was trying to find where the existing callers have their RM and it is not obvious.

tstuefe · 2024-06-20T08:29:43Z

Thanks @MBaesken and @dholmes-ora !

/integrate

openjdk · 2024-06-20T08:30:55Z

Going to push as commit c6f3bf4.
Since your change was applied there have been 92 commits pushed to the master branch:

cabd104: 8334164: The fix for JDK-8322811 should use _filename.is_set() rather than strcmp()
d7dad50: 8334544: C2: wrong control assigned in PhaseIdealLoop::clone_assertion_predicate_for_unswitched_loops()
ff30240: 8334239: Introduce macro for ubsan method/function exclusions
2d4185f: 8332717: ZGC: Division by zero in heuristics
fad6644: 8333754: Add a Test against ECDSA and ECDH NIST Test vector
b211929: 8334570: Problem list gc/TestAlwaysPreTouchBehavior.java
4e58d8c: 8309821: Link to hidden classes section in Class specification for Class::isHidden
78682fe: 8329288: Update Visual Studio visibility support for POSIX functions
bcf4bb4: 8333344: JMX attaching of Subject does not work when security manager not allowed
856931d: 8304732: jdk/jfr/api/consumer/recordingstream/TestStop.java failed again with "Expected outer stream to have 3 events"
... and 82 more: https://git.openjdk.org/jdk/compare/aaaa86b57172d45d1126c50efc270c6e49aba7a5...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-06-20T08:31:01Z

@tstuefe Pushed as commit c6f3bf4.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

JDK-8334026-Provide-a-diagnostic-PrintMemoryMapAtExit-switch-on-Linux

2784875

fix whitespaces

2b3a3f9

openjdk bot changed the title ~~JDK-8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux~~ 8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux Jun 11, 2024

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Jun 11, 2024

tstuefe marked this pull request as ready for review June 12, 2024 07:06

openjdk bot added the rfr Pull request is ready for review label Jun 12, 2024

dholmes-ora reviewed Jun 14, 2024

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feedback david

f03983b

dholmes-ora approved these changes Jun 18, 2024

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MBaesken approved these changes Jun 20, 2024

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openjdk bot closed this Jun 20, 2024

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8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux #19660

8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux #19660

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8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux #19660

8334026: Provide a diagnostic PrintMemoryMapAtExit switch on Linux #19660

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