JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 #16261

tstuefe · 2023-10-19T07:50:11Z

See JBS issue.

The real fix, trivial, is the comparison change in compressedKlass.cpp.

This patch then also adds a test that checks that for a given (forced) class space location the VM chose the correct encoding scheme. In this case, if class space nestles below and ends at 4G, we should use a shift of 0.

The test can be easily extended to test more narrow Klass encoding schemes. Note that the test is skipped if the VM could not map at the expected address to begin with.

Finally, to analyze test errors, I print out the mappings at the force address if metaspace logging is debug.

Tests: manual, GHA. x86 GHA errors unrelated.

/label remove core-libs
/label remove hotspot
/label add hotspot-runtime

Attention @iklam and @calvinccheung

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JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 (Bug - P4)

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Calvin Cheung (@calvinccheung - Reviewer)
Ioi Lam (@iklam - Reviewer)

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bridgekeeper · 2023-10-19T07:51:29Z

👋 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 · 2023-10-19T07:55:00Z

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

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hotspot

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

openjdk · 2023-10-20T05:43:05Z

@tstuefe
The core-libs label was successfully removed.

openjdk · 2023-10-20T05:43:53Z

@tstuefe
The hotspot label was successfully removed.

openjdk · 2023-10-20T05:44:34Z

@tstuefe
The hotspot-runtime label was successfully added.

mlbridge · 2023-10-20T05:47:47Z

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01: Full - Incremental (b87f88f9)
00: Full (8b6f5338)

calvinccheung

Thanks for fixing this. I've tried your patch on the CompressedClassPointers.java test. It also fixes the issue in JDK-8317610. Just have a couple of minor comments.

calvinccheung · 2023-10-20T23:04:39Z

src/hotspot/share/memory/metaspace.cpp

+          LogStream ls(lt);
+          os::print_memory_mappings((char*)base, size, &ls);


I saw the above log message as follows:

java -XX:+UnlockDiagnosticVMOptions -XX:CompressedClassSpaceBaseAddress=0xa0000000 -XX:CompressedClassSpaceSize=1g -Xlog:metaspace=debug -Xlog:os+map=trace -Xshare:off -version [0.001s][info][metaspace] - commit_granule_bytes: 65536. [0.001s][info][metaspace] - commit_granule_words: 8192. [0.001s][info][metaspace] - virtual_space_node_default_size: 8388608. [0.001s][info][metaspace] - enlarge_chunks_in_place: 1. [0.001s][info][metaspace] - use_allocation_guard: 0. [0.036s][debug][metaspace] Range [a0000000-e0000000) contains: [0.036s][debug][metaspace] a0000000-120000000 rw-p 00000000 00:00 0 [0.036s][debug][metaspace] Error occurred during initialization of VM CompressedClassSpaceBaseAddress=0x00000000a0000000 given, but reserving class space failed.

Is it easy to get rid of the blank line before the line begins with "Error occurred..."?

calvinccheung · 2023-10-20T23:06:51Z

test/hotspot/jtreg/runtime/CompressedOops/CompressedClassPointersEncodingScheme.java

+        // Expecting base=0, shift=0
+        test(4 * G - 128 * M, 128 * M, 0, 0);
+
+        // add more...


The following works on my linux dev host.

test(0xa0000000L, 1 * G, 0, 0); test(0x100000000L, 2 * G, 0, 3);

Maybe you can consider adding them to the test?

I'd rather expand this in a separate RFE. Second one should work on all platforms, but I am not 100% sure some would encode this with base=4g shift=0 instead. Probably not, but it is better to stay focused on one issue. Makes also for clearer backporting.

That's fine.

tstuefe · 2023-10-23T12:10:06Z

Thanks @calvinccheung . I fixed the output as requested.

calvinccheung

Thanks for the update. It looks good.

openjdk · 2023-10-23T15:51:51Z

@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:

8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000

Reviewed-by: ccheung, iklam

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 73 new commits pushed to the master branch:

8d9a4b4: 8317678: Fix up hashCode() for ZipFile.Source.Key
69c0ae2: 8318124: JFR: Rewrite instrumentation to use Class-File API
c1aeac7: 8318445: More broken bailout chains in C2
d888b26: 8318071: IgnoreUnrecognizedVMOptions flag still causes failure in ArchiveHeapTestClass
bea2d48: 8312475: org.jline.util.PumpReader signed byte problem
9f767aa: 8318109: Writing JFR records while a CHT has taken its lock asserts in rank checking
bd22d23: 8318027: Support alternative name to jdk.internal.vm.compiler
c2efd77: 8295795: hsdis does not build with binutils 2.39+
99de9bb: 8317807: JAVA_FLAGS removed from jtreg running in JDK-8317039
704c6ea: 8303525: Refactor/cleanup open/test/jdk/javax/rmi/ssl/SSLSocketParametersTest.java
... and 63 more: https://git.openjdk.org/jdk/compare/6fc35142315f1616fa35e415005c9483939c6920...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.

iklam

LGTM

tstuefe · 2023-10-23T21:08:44Z

Thanks @calvinccheung and @iklam .

/integrate

openjdk · 2023-10-23T21:10:58Z

Going to push as commit 5ba9705.
Since your change was applied there have been 73 commits pushed to the master branch:

8d9a4b4: 8317678: Fix up hashCode() for ZipFile.Source.Key
69c0ae2: 8318124: JFR: Rewrite instrumentation to use Class-File API
c1aeac7: 8318445: More broken bailout chains in C2
d888b26: 8318071: IgnoreUnrecognizedVMOptions flag still causes failure in ArchiveHeapTestClass
bea2d48: 8312475: org.jline.util.PumpReader signed byte problem
9f767aa: 8318109: Writing JFR records while a CHT has taken its lock asserts in rank checking
bd22d23: 8318027: Support alternative name to jdk.internal.vm.compiler
c2efd77: 8295795: hsdis does not build with binutils 2.39+
99de9bb: 8317807: JAVA_FLAGS removed from jtreg running in JDK-8317039
704c6ea: 8303525: Refactor/cleanup open/test/jdk/javax/rmi/ssl/SSLSocketParametersTest.java
... and 63 more: https://git.openjdk.org/jdk/compare/6fc35142315f1616fa35e415005c9483939c6920...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-10-23T21:11:04Z

@tstuefe Pushed as commit 5ba9705.

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

JDK-8318485

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openjdk bot added hotspot hotspot-dev@openjdk.org core-libs core-libs-dev@openjdk.org labels Oct 19, 2023

Update CompressedClassPointersEncodingScheme.java

8b6f533

tstuefe marked this pull request as ready for review October 20, 2023 05:41

openjdk bot added rfr Pull request is ready for review and removed core-libs core-libs-dev@openjdk.org labels Oct 20, 2023

openjdk bot removed the hotspot hotspot-dev@openjdk.org label Oct 20, 2023

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Oct 20, 2023

calvinccheung reviewed Oct 20, 2023

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feedback calvin

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JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 #16261

JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 #16261

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		LogStream ls(lt);
		os::print_memory_mappings((char*)base, size, &ls);

JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 #16261

JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 #16261

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