8306695: Divide by zero in G1Policy::logged_cards_processing_time

[kimbarrett]

Please review this change to G1Policy::logged_cards_processing_time to avoid a
floating point division by zero when both the number of logged cards and the
total cards processed are zero. This happens during early GCs. The fix is to
change the comparison used to decide between scaling the total time vs
ascribing all of the time to the logged cards. It is changed from ">" to ">="
so that it also covers the case of both values being zero.

Testing:
mach5 tier1
Local build with UBSAN and verified there are no longer any division by zero
errors reported by it.

---

Progress

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• Commit message must refer to an issue

Issue

• JDK-8306695: Divide by zero in G1Policy::logged_cards_processing_time

Reviewers

• Ivan Walulya (@walulyai - Reviewer) ⚠️ Review applies to 5d00bd2f
• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to 5d00bd2f

Reviewing

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (7a6ac793)
• 00: Full (5d00bd2f)

[openjdk]

@kimbarrett 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:

8306695: Divide by zero in G1Policy::logged_cards_processing_time

Reviewed-by: iwalulya, tschatzl

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

• 2471919: 8304036: Use CommandLine class from shared module

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[kimbarrett]

Thanks @tschatzl and @walulyai for reviews.

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 8063aa2.
Since your change was applied there has been 1 commit pushed to the master branch:

• 2471919: 8304036: Use CommandLine class from shared module

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit 8063aa2.

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