On Wed, 6 Nov 2024 14:15:42 GMT, jengebr <d...@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
Changes requested by liach (Reviewer).
src/java.base/share/classes/java/lang/PublicMethods.java line 108:
> 106: Class<?>[] ptypes) {
> 107: // check for matching param types length, then name, then
> param type equality
> 108: return method.getParameterCount() == ptypes.length &&
Length check is already present in `equals`. If you want this fast path, I
think moving arrays equals check first is better.
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()`.
-------------
PR Review: https://git.openjdk.org/jdk/pull/21929#pullrequestreview-2418640017
PR Review Comment: https://git.openjdk.org/jdk/pull/21929#discussion_r1831230782
PR Review Comment: https://git.openjdk.org/jdk/pull/21929#discussion_r1831232688
