8345942: Separate source output from class output when building microbenchmarks

[lahodaj]

The microbenchmarks build generates a considerable amount of (generated) sources using an annotation processor. This, by itself, is not a problem. But, it generates them into the class output, and after the microbenchmarks build has been updated to be (somewhat) incremental, the class output has been added to the classpath(*):
b704bfa

Then when the AP attempts to generate a new file (for a class name), javac will look for same-named classes on the classpath, and may load the source code generated by a previous rounds of builds, in case of an incremental build. And since the AP generates the considerable amount of these files, this leads to loading a considerable amounts of source code, eventually leading to memory problems (JDK-8345302).

The proposal herein is to split the (generated) source output from the class output. This considerably reduces the amount of memory javac uses, and generally seems like a good approach for the build.

(*) adding the class output to the classpath is usually needed when incrementally compiling code in the unnamed module, to ensure that if e.g. only one source file is being compiled, it can refer to other, already produced, classes. As a side note, this does not need to be done in named-module compilation modes, as javac automatically reads the class output when compiling the named modules. But it is not easily possible to enhance javac to do that for unnamed module, due to compatibility concerns.

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Issue

• JDK-8345942: Separate source output from class output when building microbenchmarks (Bug - P4)

Reviewers

• Aleksey Shipilev (@shipilev - Reviewer)
• Erik Joelsson (@erikj79 - Reviewer)

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[openjdk]

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

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

8345942: Separate source output from class output when building microbenchmarks

Reviewed-by: shade, erikj

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At the time when this comment was updated there had been 96 new commits pushed to the master branch:

• 18d1d61: 8346046: Enable copyright header format check
• a7631cc: 8346235: RISC-V: Optimize bitwise AND with mask values
• 929d4a5: 8346231: RISC-V: Fix incorrect assertion in SharedRuntime::generate_handler_blob
• 3030230: 8346278: Clean up some flag handing in flags-cflags.m4
• fd0207d: 8345327: JDK 24 RDP1 L10n resource files update
• 31c3b19: 8346174: UMAX/UMIN are missing from XXXVector::reductionOperations
• c75b1d4: 8346082: Output JVMTI agent information in hserr files
• 51662c2: 8346232: Remove leftovers of the jar --normalize feature
• d335941: 8345678: compute_modifiers should not be in create_mirror
• 57adf64: 8346261: Cleanup in JDP tests
• ... and 86 more: https://git.openjdk.org/jdk/compare/4f855d1342d55aeee93b7d0c5796fbfd4994c856...master

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[mlbridge]

Webrevs

• 00: Full (885b2228)

[shipilev]

This looks good. I think this is similar to how standard Maven-based JMH build works as well: it puts the generated sources into target/generated-sources, separate from the original sources.

[lahodaj]

/integrate

[openjdk]

Going to push as commit 99af595.
Since your change was applied there have been 103 commits pushed to the master branch:

• 8a64595: 8346282: [JVMCI] Add failure reason support to UnresolvedJava/Type/Method/Field
• 725079b: 8345506: jar --validate may lead to java.nio.file.FileAlreadyExistsException
• 5e25c48: 8346289: Confusing phrasing in IR Framework README / User-defined Regexes
• fbbc7c3: 8346120: VirtualThreadPinned event recorded for Object.wait may have wrong duration or may record second event
• 466c00a: 8346234: javax/swing/text/DefaultEditorKit/4278839/bug4278839.java still fails in CI
• bd3c0be: 8268611: jar --validate should check targeted classes in MR-JAR files
• 87804f2: 8346294: Invalid lint category specified in compiler.properties
• 18d1d61: 8346046: Enable copyright header format check
• a7631cc: 8346235: RISC-V: Optimize bitwise AND with mask values
• 929d4a5: 8346231: RISC-V: Fix incorrect assertion in SharedRuntime::generate_handler_blob
• ... and 93 more: https://git.openjdk.org/jdk/compare/4f855d1342d55aeee93b7d0c5796fbfd4994c856...master

Your commit was automatically rebased without conflicts.

[openjdk]

@lahodaj Pushed as commit 99af595.

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