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8283681: Improve ZonedDateTime offset handling #7957

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@cl4es cl4es commented Mar 25, 2022

Richard Startin prompted me to have a look at a case where java.time underperforms relative to joda time (https://twitter.com/richardstartin/status/1506975932271190017).

It seems the java.time test of his suffer from heavy allocations due ZoneOffset::getRules allocating a new ZoneRules object every time and escape analysis failing to do the thing in his test. The patch here adds a simple specialization so that when creating ZonedDateTimes using a ZoneOffset we don't query the rules at all. This removes the risk of extra allocations and slightly speeds up ZonedDateTime creation for both ZoneOffset (+14%) and ZoneRegion (+5%) even when EA works like it should (the case in the here provided microbenchmark).


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@openjdk openjdk bot added the rfr Pull request is ready for review label Mar 25, 2022
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@cl4es The following label will be automatically applied to this pull request:

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private static final TimeZone UTC = TimeZone.getTimeZone("UTC");

private static final TimeZone LONDON = TimeZone.getTimeZone("Europe/London");

private static final long[] INSTANT_MILLIS = createInstants();

private static final int[] YEARS = new int[INSTANT_MILLIS.length];

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Does it make any difference if these aren't constant?

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@cl4es cl4es Mar 25, 2022

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Interestingly a slight increase in the measured gain (14% -> 25%). I think we should favor non-constant data to subdue irrelevant JIT shenanigans so I pushed the changes.

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mlbridge bot commented Mar 25, 2022

Webrevs

@@ -507,6 +507,11 @@ public ZoneRules getRules() {
return ZoneRules.of(this);
}

@Override
/* package-private */ ZoneOffset getOffset(long epochSecond, int nanoOfSecond) {
return this;
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An alternate approach would be for ZoneOffset to cache the instance of ZoneRules either on construction or first use (racy idiom would be OK). That way this issue is solved for the many different places that call zoneId.getRules().

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@cl4es cl4es Mar 25, 2022

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Why not both? I measured an improvement using that alone, but specifically avoiding going via getRules is faster still (without adversely affecting ZoneRegion paths). I've added the cache in ZoneOffset, along with an override of ZoneId::normalized in ZoneOffset to shortcut the getRules.

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LGTM

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openjdk bot commented Mar 25, 2022

@cl4es 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:

8283681: Improve ZonedDateTime offset handling

Reviewed-by: scolebourne, naoto, rriggs

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At the time when this comment was updated there had been 4 new commits pushed to the master branch:

  • f4fd53d: 8273370: Preferences.exportSubtree() generates invalid XML if value contains control char
  • 3b5dfee: 8283665: Two Jarsigner tests needs to be updated with JDK-8267319
  • 656cba7: 8283349: Robustness improvements to java/util/prefs/AddNodeChangeListener.jar
  • f8a1649: 8274735: javax.imageio.IIOException: Unsupported Image Type while processing a valid JPEG image

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As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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@openjdk openjdk bot added the ready Pull request is ready to be integrated label Mar 25, 2022
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cl4es commented Mar 25, 2022

Thanks for reviews!

/integrate

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openjdk bot commented Mar 25, 2022

Going to push as commit 7bac0a8.
Since your change was applied there have been 8 commits pushed to the master branch:

  • 2600f99: 8282685: fileToEncodedURL_[name|signature] symbols are unused
  • e97cf15: 8283691: Classes in java.security still reference deprecated classes in spec
  • cb012a5: 8283648: Improve the snippet "file not found" message.
  • 36b36ef: 8283661: Unexpected TypeElement in ANALYZE TaskEvent
  • f4fd53d: 8273370: Preferences.exportSubtree() generates invalid XML if value contains control char
  • 3b5dfee: 8283665: Two Jarsigner tests needs to be updated with JDK-8267319
  • 656cba7: 8283349: Robustness improvements to java/util/prefs/AddNodeChangeListener.jar
  • f8a1649: 8274735: javax.imageio.IIOException: Unsupported Image Type while processing a valid JPEG image

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Mar 25, 2022
@openjdk openjdk bot closed this Mar 25, 2022
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Mar 25, 2022
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openjdk bot commented Mar 25, 2022

@cl4es Pushed as commit 7bac0a8.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

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