<i18n dev> RFR: 8345668: ZoneOffset.ofTotalSeconds performance regression [v3]

[Shaojin Wen]

On Fri, 20 Dec 2024 21:06:16 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> The change made in [JDK-8288723](https://bugs.openjdk.org/browse/JDK-8288723) seems innocuous, but it caused this performance regression. Partially reverting the change (ones that involve `computeIfAbsent()`) to the original. Provided a benchmark that iterates the call to `ZoneOffset.ofTotalSeconds(0)` 1,000 times, which improves the operation time from 3,946ns to 2,241ns.
>
> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixed compile error

src/java.base/share/classes/java/time/ZoneOffset.java line 428:

> 426:         if (totalSeconds % (15 * SECONDS_PER_MINUTE) == 0) {
> 427:             Integer totalSecs = totalSeconds;
> 428:             ZoneOffset result = SECONDS_CACHE.get(totalSecs);

Here, each call may allocate an Integer object. The maximum number of ZoneOffsets that need to be cached here is only 148. Using AtomicReferenceArray is better than AtomicConcurrentHashMap.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22854#discussion_r1894486852