8357481: Excessive CompileTask wait/notify monitor creation

[shipilev]

See bug for rationale.

This PR implements the 2nd solution from the bug: lift the lock to be global. As described in the bug, excess locking work would realistically affect Xcomp, and only in a minor way. But we will reap a minor footprint/latency benefit by not constructing the lock for every CompileTask.

Additional testing:

• Linux x86_64 server fastdebug, compiler
• Linux x86_64 server fastdebug, all
• Linux AArch64 server fastdebug, all

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Progress

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Issue

• JDK-8357481: Excessive CompileTask wait/notify monitor creation (Enhancement - P4)

Reviewers

• Vladimir Ivanov (@iwanowww - Reviewer)
• Vladimir Kozlov (@vnkozlov - Reviewer)

Reviewing

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[openjdk]

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

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8357481: Excessive CompileTask wait/notify monitor creation

Reviewed-by: vlivanov, kvn

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• 28f5093: 8356233: NMT: tty->print_cr should not be used in VirtualMemoryTracker::add_reserved_region()

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[mlbridge]

Webrevs

• 02: Full - Incremental (6a8955d8)
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• 00: Full (65ad15e0)

[shipilev]

Testing is all green here. Waiting for reviews :)

[dean-long]

Isn't it true that we only have one CompileTask per CompilerThread? Would it make sense to move this monitor into the CompilerThread instead?

[iwanowww]

Looks good.

[shipilev]

Isn't it true that we only have one CompileTask per CompilerThread? Would it make sense to move this monitor into the CompilerThread instead?

It feels awkward to me to have a logically CompileTask-related monitor in CompilerThread. Among other things, this will tie the lifecycle of the compile task to the lifecycle of the compiler thread, which gets "interesting" with dynamic number of compiler threads. Plus, I don't think any of this optimization would matter for non-Xcomp runs. So I'd steer towards simplicity, and just make this monitor global, as in this PR.

[vnkozlov]

Good.

[shipilev]

Thanks! I think I'll wait for AOT JEPs to land into mainline first, to avoid breaking them accidentally. Do you know when those integrate?

[vnkozlov]

Thanks! I think I'll wait for AOT JEPs to land into mainline first, to avoid breaking them accidentally. Do you know when those integrate?

Waiting PIT testing results.

[shipilev]

I see AOT profiles JEP landed in mainline. Re-merged (cleanly) from current master, re-ran some tests.

[vnkozlov]

Is this ready for retesting?

[shipilev]

Is this ready for retesting?

Yes, please. There is a long weekend in Germany, so I think I'll integrate only next week, though.

[vnkozlov]

Is this ready for retesting?

Yes, please. There is a long weekend in Germany, so I think I'll integrate only next week, though.

I started testing.

[vnkozlov]

My testing passed without new failures.

[shipilev]

Thanks for testing! I remerged locally with current master, ran tier1 and compiler tests, and there are no troubles. So I am integrating.

/integrate

[openjdk]

Going to push as commit b3594c9.
Since your change was applied there have been 76 commits pushed to the master branch:

• 83b15da: 8351997: AArch64: Interpreter volatile reference stores with G1 are not sequentially consistent
• c22af0c: 8358205: Remove unused JFR array allocation code
• 83cb0c6: 8358151: Harden JSR166 Test case testShutdownNow_delayedTasks
• ... and 73 more: https://git.openjdk.org/jdk/compare/cd052c72cdb62186e66c1d2ecf9216f3df61b242...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit b3594c9.

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