8264846: Regression ~5% in J2dBench.bimg_misc on Linux after JDK-8263142

[mrserb]

Performance in one of the tests in the bimg_misc group is dropped by 20%(or 5% of the group) after some unused code was removed from the libawt. I assume the size of the lib became smaller and GCC heuristics were changed to do not try to increase the size by inlining over some percent. I tested various options but most of them affect different test cases in the opposite ways.

While testing I have found that the most profitable option is to simply use the "O3" optimization level, moreover, after offline discussion, we have found that this optimization level was used before, but due to the typo, we missed this option and fallback to the "LOW" level.

Note this will change optimization level for all platforms in case of any regressions we may try to implement this change for GGC only or we may try to use just these options to solve this performance issue: " -ftree-loop-vectorize -fversion-loops-for-strides "

Summary:
  b12:
    Number of tests: 13
    Overall average: 1222067.1646119351
    Best spread: 0.07% variance
    Worst spread: 3.22% variance
    (Basis for results comparison)

  o3:
    Number of tests: 13
    Overall average: 1991716.540920269
    Best spread: 0.0% variance
    Worst spread: 2.22% variance
    Comparison to basis:
      Best result: 314.15% of basis
      Worst result: 97.23% of basis
      Number of wins: 8
      Number of ties: 4
      Number of losses: 1

  two options:
    Number of tests: 13
    Overall average: 1971528.6542701898
    Best spread: 0.0% variance
    Worst spread: 7.08% variance
    Comparison to basis:
      Best result: 312.05% of basis
      Worst result: 77.27% of basis
      Number of wins: 6
      Number of ties: 1
      Number of losses: 6

---

Progress

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Issue

• JDK-8264846: Regression ~5% in J2dBench.bimg_misc on Linux after JDK-8263142

Reviewers

• Erik Joelsson (@erikj79 - Reviewer)
• Alexander Zvegintsev (@azvegint - Reviewer)

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8264846: Regression ~5% in J2dBench.bimg_misc on Linux after JDK-8263142

Reviewed-by: erikj, azvegint

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At the time when this comment was updated there had been 10 new commits pushed to the master branch:

• b4371e9: 8266552: Technical corrections to java/util/random/package-info.java
• e14b026: 8243287: Removal of Unsafe::defineAnonymousClass
• a564f2c: 8266821: G1: Prefetch cards during merge heap roots phase
• 127bfe4: 8266074: Vtable-based CHA implementation
• 347d41d: 8164804: sun/security/ssl/SSLSocketImpl/CloseSocket.java makes not reliable time assumption
• 17ceef9: 8266819: Separate the stop policies from the compile policies completely
• a270cbe: 8267043: IntelliJ project doesn't handle generated sources correctly
• 08a5a5c: 8263382: java/util/logging/ParentLoggersTest.java failed with "checkLoggers: getLoggerNames() returned unexpected loggers"
• b50fc5f: 8265528: Specification of BasicSplitPaneDivider::getMinimumSize,getPreferredSize doesn't match with its behavior.
• d215743: 8231031: runtime/ReservedStack/ReservedStackTest.java fails after jsr166 refresh

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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[mrserb]

/integrate

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@mrserb Since your change was applied there have been 16 commits pushed to the master branch:

• 2a2f105: 8267117: sun/hotspot/whitebox/CPUInfoTest.java fails on Ice Lake
• 2667024: 8266881: Enable debug log for SSLEngineExplorerMatchedSNI.java
• 6c107fd: 8264299: Create implementation of native accessibility peer for ScrollPane and ScrollBar Java Accessibility roles
• 853ffdb: 8265934: Cleanup _suspend_flags and _special_runtime_exit_condition
• f3c6cda: 8266162: Remove JPackage duplicate tests
• a259ab4: 8258795: Update IANA Language Subtag Registry to Version 2021-05-11
• b4371e9: 8266552: Technical corrections to java/util/random/package-info.java
• e14b026: 8243287: Removal of Unsafe::defineAnonymousClass
• a564f2c: 8266821: G1: Prefetch cards during merge heap roots phase
• 127bfe4: 8266074: Vtable-based CHA implementation
• ... and 6 more: https://git.openjdk.java.net/jdk/compare/ab17be283559ba0477bc0dcbd11dbfccf155a57f...master

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