8357600: Patch nmethod flushing message to include more details

[JohnTortugo]

Please review this patch for adding more details to nmethod flushing message. These details are particularly important when investigating interaction of JVMCI compiled code and code cache flushing heuristics.

Tested on Linux x64 with JTREG tier1-3 using fastdebug and release builds.

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Issue

• JDK-8357600: Patch nmethod flushing message to include more details (Enhancement - P4)

Reviewers

• Aleksey Shipilev (@shipilev - Reviewer)
• Vladimir Kozlov (@vnkozlov - Reviewer)

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

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8357600: Patch nmethod flushing message to include more details

Reviewed-by: shade, kvn

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At the time when this comment was updated there had been 855 new commits pushed to the master branch:

• a44a470: 8358515: make cmp-baseline is broken after JDK-8349665
• cc11b7d: 8356128: Correct documentation for --linux-package-deps
• 406f1bc: 8357650: ThreadSnapshot to take snapshot of thread for thread dumps
• ... and 852 more: https://git.openjdk.org/jdk/compare/a2d7f441b8616e0cd8c231f3358b1b508e76686d...master

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[shipilev]

A bit concerned about performance impact of this logging, especially since we are under CodeCache_lock. So I would suggest two improvements:

1. Maybe move logging before acquiring CodeCache_lock? Not sure if it is safe for various CodeCache::* getters.

2. Predicate the argument preparation/logging with:

  LogTarget(Debug, codecache) lt;
  if (lt.is_enabled()) {
    ...

[JohnTortugo]

Thank you for the comments @shipilev . TBH I totally overlooked that lock there and I didn't know about the LogTarget::is_enabled()

[JohnTortugo]

@shipilev - I made changes following your suggestion. I moved the printing to before acquiring the lock and I also moved it to under a if checking if logging is enabled. I don't think these get/logging operation in particular need to be under a lock.

[shipilev]

Not sure about calling is_cold() without a lock: looks like _gc_epoch counter is unsynchronized. Now that you predicated the bulk of the logging with logging checks, I think it is fine to grab CodeCache_lock before doing logging.

[shipilev]

Looks OK to me. This is a diagnostic logging, so we do not have to be extra crisp about it. Let any other compiler folks review as well.

[vnkozlov]

Good.

[JohnTortugo]

/integrate

[openjdk]

Going to push as commit 2345065.
Since your change was applied there have been 860 commits pushed to the master branch:

• 9c74d54: 8358158: test/jdk/java/io/Console/CharsetTest.java failing with NoClassDefFoundError: jtreg/SkippedException
• 9397535: 8356803: Test TextLayout/TestControls fails on windows & linux: line and paragraph separator show non-zero advance
• da49fa5: 8354460: Streaming output for attach API should be turned on by default
• ... and 857 more: https://git.openjdk.org/jdk/compare/a2d7f441b8616e0cd8c231f3358b1b508e76686d...master

Your commit was automatically rebased without conflicts.

[openjdk]

@JohnTortugo Pushed as commit 2345065.

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