On Wed, 6 Nov 2024 15:20:42 GMT, Chen Liang <li...@openjdk.org> wrote:
>> This change optimizes the runtime of `Class.getMethod(String, Class<?>[])`
>> in two ways:
>>
>> 1. While iterating across each Method to find a match (existing logic) it
>> now compares parameter count before checking method name. This check is
>> substantially faster.
>> 2. While iterating (existing logic) if the requested method has no
>> arguments, the loop terminates early after finding one match. This works
>> because there can only be one zero-arg method with the matching name in the
>> specific class.
>>
>> A benchmark and unit tests are included; benchmark results (below) show an
>> improvement in all cases, and an especially large gain when the immediate
>> class contains the no-arg target.
>>
>> Base:
>>
>> Benchmark Mode Cnt Score Error Units
>> ClassGetMethod.getConcreteFiveArg avgt 6 90.866 ± 2.698 ns/op
>> ClassGetMethod.getConcreteNoArg avgt 6 72.472 ± 10.225 ns/op
>> ClassGetMethod.getIntfFiveArg avgt 6 198.524 ± 7.089 ns/op
>> ClassGetMethod.getIntfNoArg avgt 6 191.739 ± 4.695 ns/op
>> ClassGetMethod.getNoSuchMethod avgt 10 2254.308 ± 42.829 ns/op
>> ClassGetMethod.getSuperFiveArg avgt 6 165.897 ± 4.370 ns/op
>> ClassGetMethod.getSuperNoArg avgt 6 148.361 ± 4.573 ns/op
>>
>>
>> Modified:
>>
>> Benchmark Mode Cnt Score Error Units
>> ClassGetMethod.getConcreteFiveArg avgt 6 77.059 ± 2.644 ns/op
>> ClassGetMethod.getConcreteNoArg avgt 6 47.666 ± 6.544 ns/op
>> ClassGetMethod.getIntfFiveArg avgt 6 164.427 ± 4.356 ns/op
>> ClassGetMethod.getIntfNoArg avgt 6 161.256 ± 6.832 ns/op
>> ClassGetMethod.getNoSuchMethod avgt 10 2158.844 ± 43.716 ns/op
>> ClassGetMethod.getSuperFiveArg avgt 6 129.047 ± 4.414 ns/op
>> ClassGetMethod.getSuperNoArg avgt 6 123.728 ± 6.182 ns/op
>
> src/java.base/share/classes/java/lang/PublicMethods.java line 157:
>
>> 155: head = tail = new MethodList(method);
>> 156: if (ptypes.length == 0) {
>> 157: // zero args can only have one match - stop
>> looking
>
> This is wrong: if superclass has `Object work()` and this class has `Integer
> work()`, bytecode for this class will have a synthetic final `Object work()`
> that delegates call to `Integer work()`.
Gotcha, I'll remove the no-arg change. Thanks!
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/21929#discussion_r1831250497
