8368321: Rethink compilation delay strategy for lukewarm methods

[veresov]

In the current implementation we delay profiling of lukewarm methods (those that were never compiled by C2 during training) by increasing the 2->3 threshold by a factor. That may shift profiling of those too much into the future if a large factor is used, if we use a small factor, however, profiling may happen within the training run window so to speak. The solution I came up with it to delay profiling until we reach the number of invocations of a method equal to the number we had in the training run. After that we use the normal policy.

Here is an example. I trained our JavacBenchApp for 5 iterations (which is artificially low and therefore many methods would be classified as lukewarm). Then I ran it for 200 iterations with AOT replay.

While initially the performance is similar it quickly diverges. With the new approach we move to standard handling of lukewarm methods after 5 iterations and they get compiled with C2. With the old approach we don't.

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Issue

• JDK-8368321: Rethink compilation delay strategy for lukewarm methods (Enhancement - P3)

Reviewers

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

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8368321: Rethink compilation delay strategy for lukewarm methods

Reviewed-by: kvn, vlivanov

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At the time when this comment was updated there had been 286 new commits pushed to the master branch:

• 97e5ac6: 8370514: Problemlist nio/channels/AsyncCloseAndInterrupt until JDK-8368290 is resolved
• 2ee3439: 8368975: Windows ProcessImpl.java has dead code
• 13adcd9: 8274082: Wrong test name in jtreg run tag for java/awt/print/PrinterJob/SwingUIText.java
• ... and 283 more: https://git.openjdk.org/jdk/compare/0f2a95c15d7c1e3796660d786c9a72497dab5ab1...master

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Webrevs

• 01: Full - Incremental (0ecea581)
• 00: Full (e5d944af)

[veresov]

Testing looks ok

[vnkozlov]

Seems fine.

[iwanowww]

Looks good.