On Wed, 1 Jun 2022 13:03:38 GMT, Claes Redestad wrote:
>> When generating `MethodHandle`-based concatenation expressions in
>> `StringConcatFactory` we can reduce the number of classes generated at
>> runtime by creating small batches of prependers and mixers before binding
>> them into the root expression tree.
>>
>> Improvements on one-off tests are modest, while the improvement on
>> bootstrapping stress tests can be substantial
>> ([MixedStringCombinations.java](https://gist.github.com/cl4es/08fb581dece3a73e89bfa52337bc4248)):
>>
>> | Build |# classes| Runtime |
>> | --- | - | --- |
>> | Baseline | 31119 | 2.942s |
>> | Patch | 16208 | 1.958s |
>>
>> An earlier version of this patch saw a regression in the
>> `StringConcatFactoryBootstraps` microbenchmark. After some refactoring along
>> with the optimizations in #8881 and #8923 that is no longer the case, and
>> allocation pressure is down slightly compared to the baseline on such a
>> repeat-the-same-bootstrap stress test:
>>
>> Baseline:
>>
>> Benchmark Mode Cnt
>> Score Error Units
>> SCFB.makeConcatWithConstants avgt5
>> 2170.039 ? 117.441 ns/op
>> SCFB.makeConcatWithConstants:?gc.alloc.rate.norm avgt5
>> 3538.020 ?4.558B/op
>>
>> This patch:
>>
>> Benchmark Mode Cnt
>> Score Error Units
>> SCFB.makeConcatWithConstants avgt5
>> 2144.807 ? 162.685 ns/op
>> SCFB.makeConcatWithConstants:?gc.alloc.rate.norm avgt5
>> 3184.943 ?4.495B/op
>
> Claes Redestad has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Improve bootstrap microbenchmark to include more shapes, reduce runtime
src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 674:
> 672: 1 + pos, 2 + pos, 3 + pos, 4 + pos // selected
> arguments
> 673: );
> 674: }
This should probably also use a switch like the above:
Suggestion:
return switch (count) {
case 1 -> MethodHandles.foldArgumentsWithCombiner(mh, 0, mix,
1 + pos // selected arguments
);
case 2 -> MethodHandles.foldArgumentsWithCombiner(mh, 0, mix,
1 + pos, 2 + pos // selected arguments
);
case 3 -> MethodHandles.foldArgumentsWithCombiner(mh, 0, mix,
1 + pos, 2 + pos, 3 + pos // selected arguments
);
case 4 -> MethodHandles.foldArgumentsWithCombiner(mh, 0, mix,
1 + pos, 2 + pos, 3 + pos, 4 + pos // selected arguments
);
default -> throw new AssertionError(count);
}
-
PR: https://git.openjdk.java.net/jdk/pull/8855
