On Thu, 22 Apr 2021 14:07:20 GMT, Сергей Цыпанов <github.com+10835776+stsypa...@openjdk.org> wrote:
> Hello, from discussion in https://github.com/openjdk/jdk/pull/3464 I've found > out, that in a few of JDK core classes, e.g. in `j.l.Class` expressions like > `baseName.replace('.', '/') + '/' + name` are not compiled into > `invokedynamic`-based code, but into one using `StringBuilder`. This happens > due to some bootstraping issues. > > However the code like > > private String getSimpleName0() { > if (isArray()) { > return getComponentType().getSimpleName() + "[]"; > } > //... > } > > can be improved via replacement of `+` with `String.concat()` call. > > I've used this benchmark to measure impact: > > @State(Scope.Thread) > @BenchmarkMode(Mode.AverageTime) > @OutputTimeUnit(TimeUnit.NANOSECONDS) > @Fork(jvmArgsAppend = {"-Xms2g", "-Xmx2g"}) > public class ClassMethodsBenchmark { > private final Class<? extends Object[]> arrayClass = Object[].class; > private Method descriptorString; > > @Setup > public void setUp() throws NoSuchMethodException { > //fore some reason compiler doesn't allow me to call > Class.descriptorString() directly > descriptorString = Class.class.getDeclaredMethod("descriptorString"); > } > > @Benchmark > public Object descriptorString() throws Exception { > return descriptorString.invoke(arrayClass); > } > > @Benchmark > public Object typeName() { > return arrayClass.getTypeName(); > } > } > > and got those results > > Mode Cnt Score > Error Units > descriptorString avgt 60 91.480 ± > 1.839 ns/op > descriptorString:·gc.alloc.rate.norm avgt 60 404.008 ± > 4.033 B/op > descriptorString:·gc.churn.G1_Eden_Space avgt 60 2791.866 ± > 181.589 MB/sec > descriptorString:·gc.churn.G1_Eden_Space.norm avgt 60 401.702 ± > 26.047 B/op > descriptorString:·gc.churn.G1_Survivor_Space avgt 60 0.003 ± > 0.001 MB/sec > descriptorString:·gc.churn.G1_Survivor_Space.norm avgt 60 ≈ 10⁻³ > B/op > descriptorString:·gc.count avgt 60 205.000 > counts > descriptorString:·gc.time avgt 60 216.000 > ms > > patched > Mode Cnt Score > Error Units > descriptorString avgt 60 65.016 ± > 3.446 ns/op > descriptorString:·gc.alloc.rate avgt 60 2844.240 ± > 115.719 MB/sec > descriptorString:·gc.alloc.rate.norm avgt 60 288.006 ± > 0.001 B/op > descriptorString:·gc.churn.G1_Eden_Space avgt 60 2832.996 ± > 206.939 MB/sec > descriptorString:·gc.churn.G1_Eden_Space.norm avgt 60 286.955 ± > 17.853 B/op > descriptorString:·gc.churn.G1_Survivor_Space avgt 60 0.003 ± > 0.001 MB/sec > descriptorString:·gc.churn.G1_Survivor_Space.norm avgt 60 ≈ 10⁻³ > B/op > descriptorString:·gc.count avgt 60 208.000 > counts > descriptorString:·gc.time avgt 60 228.000 > ms > ----------------- > typeName avgt 60 34.273 ± > 0.480 ns/op > typeName:·gc.alloc.rate avgt 60 3265.356 ± > 45.113 MB/sec > typeName:·gc.alloc.rate.norm avgt 60 176.004 ± > 0.001 B/op > typeName:·gc.churn.G1_Eden_Space avgt 60 3268.454 ± > 134.458 MB/sec > typeName:·gc.churn.G1_Eden_Space.norm avgt 60 176.109 ± > 6.595 B/op > typeName:·gc.churn.G1_Survivor_Space avgt 60 0.003 ± > 0.001 MB/sec > typeName:·gc.churn.G1_Survivor_Space.norm avgt 60 ≈ 10⁻⁴ > B/op > typeName:·gc.count avgt 60 240.000 > counts > typeName:·gc.time avgt 60 255.000 > ms > > patched > > typeName avgt 60 15.787 ± > 0.214 ns/op > typeName:·gc.alloc.rate avgt 60 2577.554 ± > 32.339 MB/sec > typeName:·gc.alloc.rate.norm avgt 60 64.001 ± > 0.001 B/op > typeName:·gc.churn.G1_Eden_Space avgt 60 2574.039 ± > 147.774 MB/sec > typeName:·gc.churn.G1_Eden_Space.norm avgt 60 63.895 ± > 3.511 B/op > typeName:·gc.churn.G1_Survivor_Space avgt 60 0.003 ± > 0.001 MB/sec > typeName:·gc.churn.G1_Survivor_Space.norm avgt 60 ≈ 10⁻⁴ > B/op > typeName:·gc.count avgt 60 189.000 > counts > typeName:·gc.time avgt 60 199.000 > ms > > I think this patch is likely to improve reflection operations related to > arrays. > > If one finds this patch useful, then I'll create a ticket to track this. Also > it'd be nice to have a list of classes, that are compiled in the same way as > `j.l.Class` (i.e. have no access to `invokedynamic`) so I could look into > them for other snippets where two String are joined so `concat`-based > optimization is possible. > > Pre-sizing of `StringBuilder` for `Class.gdescriptorString()` and > `Class.getCanonicalName0()` is one more improvement opportunity here. This pull request has now been integrated. Changeset: 6c4c48fa Author: Sergey Tsypanov <sergei.tsypa...@yandex.ru> Committer: Claes Redestad <redes...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/6c4c48faea8a8309a71d7a5d261f776031014881 Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod 8266972: Use String.concat() in j.l.Class where invokedynamic-based String concatenation is not available Reviewed-by: redestad ------------- PR: https://git.openjdk.java.net/jdk/pull/3627
