8312749: Generational ZGC: Tests crash with assert(index == 0 || is_power_of_2(index)) #15288

robcasloz · 2023-08-15T12:43:56Z

This changeset ensures that the array copy stub underlying the intrinsic implementation of Object.clone only copies its (double-word aligned) payload, excluding the remaining object alignment padding words, when a non-default ObjectAlignmentInBytes value is used. This prevents the specialized ZGC stubs for Object[] array copy from processing undefined object alignment padding words as valid object pointers. For further details about the specific failure, see initial analysis by Erik Österlund and Stefan Karlsson and comments in the regression test included in this changeset.

As a side-benefit, the changeset simplifies the array size computation logic in GraphKit::new_array() by decoupling computation of header size and alignment padding size.

Testing

Functionality

tier1-3 (windows-x64, linux-x64, linux-aarch64, macosx-x64, and macosx-aarch64)
tier4-5 (windows-x64, linux-x64, linux-aarch64, macosx-x64, and macosx-aarch64; ZGC-specific tests only)
tier6-9 (linux-x64; ZGC-specific tests only)
tier1-3, and a few custom examples, applying JDK-8139457 (under review) on top of this changeset

Performance

Tested performance on the following set of OpenJDK micro-benchmarks, on linux-x64 (for both G1 and ZGC, using different ObjectAlignmentInBytes values):

openjdk.bench.java.lang.ArrayClone.byteClone
openjdk.bench.java.lang.ArrayClone.intClone
openjdk.bench.java.lang.ArrayFiddle.simple_clone
openjdk.bench.java.lang.Clone.cloneLarge
openjdk.bench.java.lang.Clone.cloneThreeDifferent

No significant regression was observed.

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8312749: Generational ZGC: Tests crash with assert(index == 0 || is_power_of_2(index)) (Bug - P3)

Reviewers

Tobias Hartmann (@TobiHartmann - Reviewer) ⚠️ Review applies to 5c56a5e5
Albert Mingkun Yang (@albertnetymk - Reviewer)
Vladimir Kozlov (@vnkozlov - Reviewer)

Contributors

Stefan Karlsson <stefank@openjdk.org>
Erik Österlund <eosterlund@openjdk.org>

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/15288/head:pull/15288
$ git checkout pull/15288

Update a local copy of the PR:
$ git checkout pull/15288
$ git pull https://git.openjdk.org/jdk.git pull/15288/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 15288

View PR using the GUI difftool:
$ git pr show -t 15288

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/15288.diff

Webrev

Link to Webrev Comment

…jAlignmentInBytes)

…ayCopy

This reverts commit 5b73ae4.

This reverts commit ddbc110.

This reverts commit eda6cf0.

bridgekeeper · 2023-08-15T12:45:18Z

👋 Welcome back rcastanedalo! 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.

robcasloz · 2023-08-15T12:45:45Z

/contributor add @stefank

robcasloz · 2023-08-15T12:45:55Z

/contributor add @fisk

openjdk · 2023-08-15T12:46:43Z

@robcasloz
Contributor Stefan Karlsson <stefank@openjdk.org> successfully added.

openjdk · 2023-08-15T12:47:25Z

@robcasloz
Contributor Erik Österlund <eosterlund@openjdk.org> successfully added.

openjdk · 2023-08-15T12:48:23Z

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

hotspot

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.

robcasloz · 2023-08-17T12:08:38Z

/label add hotspot-compiler

robcasloz · 2023-08-17T12:08:48Z

/label add hotspot-gc

openjdk · 2023-08-17T12:09:41Z

@robcasloz
The hotspot-compiler label was successfully added.

openjdk · 2023-08-17T12:10:23Z

@robcasloz
The hotspot-gc label was successfully added.

mlbridge · 2023-08-17T12:44:54Z

Webrevs

01: Full - Incremental (9b60e679)
00: Full (5c56a5e5)

TobiHartmann

Looks good to me!

src/hotspot/share/gc/shared/c2/barrierSetC2.cpp

openjdk · 2023-08-21T09:39:53Z

@robcasloz 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:

8312749: Generational ZGC: Tests crash with assert(index == 0 || is_power_of_2(index))

Co-authored-by: Stefan Karlsson <stefank@openjdk.org>
Co-authored-by: Erik Österlund <eosterlund@openjdk.org>
Reviewed-by: thartmann, ayang, kvn

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 271 new commits pushed to the master branch:

2624324: 8219567: Name of first parameter of RandomAccessFile(String,String) is inconsistent
8e4240c: 8314850: SharedRuntime::handle_wrong_method() gets called too often when resolving Continuation.enter
d9fc6b6: 8314759: VirtualThread.parkNanos timeout adjustment when pinned should be replaced
acaab6f: 8306040: HttpResponseInputStream.available() returns 1 on empty stream
76b9011: 8314656: GHA: No need for Debian ports keyring installation after JDK-8313701
e36620d: 8314554: Debian/Ubuntu should not link OpenJDK with --as-needed link option
97b94cb: 8314883: Java_java_util_prefs_FileSystemPreferences_lockFile0 write result errno in missing case
75e19e0: 8314819: [JVMCI] HotSpotJVMCIRuntime.lookupType throws unexpected ClassNotFoundException
c418933: 8313530: VM build without C2 fails after JDK-8312579
de0e46c: 8303815: Improve Metaspace test speed
... and 261 more: https://git.openjdk.org/jdk/compare/ec2f38fd389dc51dc4d8925e037a8bf2e64a3722...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.

albertnetymk

If I understand it correctly, much of the diff is to ensure that ArrayCopyNode::make (in BarrierSetC2::clone) gets the correct value for the length arg, calculated as align_up(array-length * elem-size, word-size) / word-size.

I wonder if it's possible to pass the actual array length (#slots) as length and move the merge-bytes-to-words-copying optimization to a lower level, e.g. inside conjoint_jbytes. Ofc, BarrierSetC2::clone_at_expansion and its derived siblings need to be adjusted accordingly, e.g. to use the actual elem-type.

(Preexisting: having ArrayCopyNode to cover both array and instance cloning hinders the readability, IMO.)

robcasloz · 2023-08-22T07:48:07Z

Thanks for reviewing, Tobias!

vnkozlov

Looks good.

robcasloz · 2023-08-24T09:10:54Z

Looks good.

Thanks for reviewing, Vladimir!

robcasloz · 2023-08-24T11:42:43Z

If I understand it correctly, much of the diff is to ensure that ArrayCopyNode::make (in BarrierSetC2::clone) gets the correct value for the length arg, calculated as align_up(array-length * elem-size, word-size) / word-size.

I wonder if it's possible to pass the actual array length (#slots) as length and move the merge-bytes-to-words-copying optimization to a lower level, e.g. inside conjoint_jbytes. Ofc, BarrierSetC2::clone_at_expansion and its derived siblings need to be adjusted accordingly, e.g. to use the actual elem-type.

(Preexisting: having ArrayCopyNode to cover both array and instance cloning hinders the readability, IMO.)

Thanks for looking at this, Albert! I agree that the code could benefit from some clean-up, and postponing the merge-bytes-to-words-copying optimization to at least BarrierSetC2::clone_at_expansion() is worth exploring. However, your suggested refactoring would not be trivial, so I suggest to integrate this fix as-is and address the simplification in a separate RFE. Please let me know if you agree, and, if so, I will create a separate RFE for your suggestion.

albertnetymk

I suggest to integrate this fix as-is and address the simplification in a separate RFE

Sounds reasonable.

robcasloz · 2023-08-25T07:15:03Z

Sounds reasonable.

Thanks, Albert! I created JDK-8314994 to capture your suggestions, please feel free to edit/extend the description if needed to reflect better your idea.

robcasloz · 2023-08-25T07:17:39Z

/integrate

openjdk · 2023-08-25T07:18:36Z

Going to push as commit 002b594.
Since your change was applied there have been 272 commits pushed to the master branch:

d024059: 8314951: VM build without C2 still fails after JDK-8313530
2624324: 8219567: Name of first parameter of RandomAccessFile(String,String) is inconsistent
8e4240c: 8314850: SharedRuntime::handle_wrong_method() gets called too often when resolving Continuation.enter
d9fc6b6: 8314759: VirtualThread.parkNanos timeout adjustment when pinned should be replaced
acaab6f: 8306040: HttpResponseInputStream.available() returns 1 on empty stream
76b9011: 8314656: GHA: No need for Debian ports keyring installation after JDK-8313701
e36620d: 8314554: Debian/Ubuntu should not link OpenJDK with --as-needed link option
97b94cb: 8314883: Java_java_util_prefs_FileSystemPreferences_lockFile0 write result errno in missing case
75e19e0: 8314819: [JVMCI] HotSpotJVMCIRuntime.lookupType throws unexpected ClassNotFoundException
c418933: 8313530: VM build without C2 fails after JDK-8312579
... and 262 more: https://git.openjdk.org/jdk/compare/ec2f38fd389dc51dc4d8925e037a8bf2e64a3722...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-08-25T07:18:46Z

@robcasloz Pushed as commit 002b594.

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

robcasloz added 17 commits August 4, 2023 11:28

Clarify that the currently computed size is rounded (aligned to MinOb…

20061e0

…jAlignmentInBytes)

Compute both sizes: rounded for AllocateArray and non-rounded for Arr…

e5f60a8

…ayCopy

Round up number of 8-byte words

aeeb99d

Rounding up payload size is only necessary for arrays

230e660

TEMPORARY: add additional macro-assembly comments

eda6cf0

TEMPORARY: set UseNewCode to true by default

ddbc110

TEMPORARY: print only 'oop_disjoint_arraycopy_uninit' stub code

5b73ae4

Use more accurate names

cd77b17

Remove unused variable

a8d5e90

Add a regression test

bb4ce7d

Comment and rename for clarity

d02e3a8

Round up object size at the end of the computation

36b3d06

Require GenZGC in the test

8498985

Revert "TEMPORARY: print only 'oop_disjoint_arraycopy_uninit' stub code"

8614d6a

This reverts commit 5b73ae4.

Revert "TEMPORARY: set UseNewCode to true by default"

59204fe

This reverts commit ddbc110.

Revert "TEMPORARY: add additional macro-assembly comments"

1233e80

This reverts commit eda6cf0.

Revert use of UseNewCode

875fdfd

openjdk bot added the hotspot hotspot-dev@openjdk.org label Aug 15, 2023

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Aug 17, 2023

openjdk bot added the hotspot-gc hotspot-gc-dev@openjdk.org label Aug 17, 2023

Remove extra whitespace

5c56a5e

robcasloz marked this pull request as ready for review August 17, 2023 12:38

openjdk bot added the rfr Pull request is ready for review label Aug 17, 2023

TobiHartmann approved these changes Aug 21, 2023

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src/hotspot/share/gc/shared/c2/barrierSetC2.cpp Outdated Show resolved Hide resolved

openjdk bot added the ready Pull request is ready to be integrated label Aug 21, 2023

albertnetymk reviewed Aug 21, 2023

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Remove extra whitespace

9b60e67

vnkozlov approved these changes Aug 23, 2023

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albertnetymk approved these changes Aug 24, 2023

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openjdk bot added the integrated Pull request has been integrated label Aug 25, 2023

openjdk bot closed this Aug 25, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Aug 25, 2023

8312749: Generational ZGC: Tests crash with assert(index == 0 || is_power_of_2(index)) #15288

8312749: Generational ZGC: Tests crash with assert(index == 0 || is_power_of_2(index)) #15288

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