On Sun, 18 Aug 2024 22:33:53 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> I think it is worthwhile to optimize the bootstrap scenario with less cost >> for other scenarios. > > Right, which is why we need to balance these microbenchmark speed-ups against > any added static footprint and other factors. Going through fewer but less > specialized methods can reduce runtime footprint and lead to quicker warmup, > for example. Also, @liach pointed out elsewhere the we might be able to avoid > many of these `ofDescriptor` calls with optimizations elsewhere, so perhaps > let's not go overboard here and re-measure with those optimizations in place > as it might make this work less impactful. > > On a related note: Running micros with `-Xint` and `-XX:TieredStopAtLevel=1` > can help indicate whether some optimization will be helpful during startup or > not. Often things align well, but sometimes optimizations that help peak > performance make interpreted performance worse, and vice versa. > > If we're optimizing for startup the best is obviously to check on some > startup benchmark of choice. A recent example (on Linux): `perf stat -r 50 > java -jar benchmarks.jar org.openjdk.bench.java.lang.StringConcatStartup` or > simply `make test TEST=micro:StringConcatStartup` > > FWIW I use this technique all the time to diagnose what we're doing during > startup: > https://cl4es.github.io/2018/11/23/Investigating-Startup-Using-Bytestacks.html > - it has helped me find numerous candidates for startup optimization. Main > reason I'm insisting on adding a main method to startup-centric JMH > benchmarks. All calls to ofDescriptor during the startup process come from here, which cannot be avoided in a simple way. at java.base/jdk.internal.constant.MethodTypeDescImpl.ofDescriptor(MethodTypeDescImpl.java:142) at java.base/java.lang.constant.MethodTypeDesc.ofDescriptor(MethodTypeDesc.java:60) at java.base/jdk.internal.classfile.impl.DirectMethodBuilder.methodTypeSymbol(DirectMethodBuilder.java:88) at java.base/jdk.internal.classfile.impl.TerminalCodeBuilder.setupTopLocal(TerminalCodeBuilder.java:36) at java.base/jdk.internal.classfile.impl.DirectCodeBuilder.<init>(DirectCodeBuilder.java:133) at java.base/jdk.internal.classfile.impl.DirectCodeBuilder.build(DirectCodeBuilder.java:106) at java.base/jdk.internal.classfile.impl.DirectMethodBuilder.withCode(DirectMethodBuilder.java:123) at java.base/jdk.internal.classfile.impl.DirectMethodBuilder.withCode(DirectMethodBuilder.java:130) at java.base/java.lang.invoke.InvokerBytecodeGenerator$5.accept(InvokerBytecodeGenerator.java:589) at java.base/java.lang.invoke.InvokerBytecodeGenerator$5.accept(InvokerBytecodeGenerator.java:567) at java.base/jdk.internal.classfile.impl.DirectMethodBuilder.run(DirectMethodBuilder.java:144) at java.base/jdk.internal.classfile.impl.DirectClassBuilder.withMethod(DirectClassBuilder.java:106) at java.base/java.lang.classfile.ClassBuilder.withMethod(ClassBuilder.java:260) at java.base/java.lang.invoke.InvokerBytecodeGenerator.methodSetup(InvokerBytecodeGenerator.java:292) at java.base/java.lang.invoke.InvokerBytecodeGenerator.addMethod(InvokerBytecodeGenerator.java:567) at java.base/java.lang.invoke.InvokerBytecodeGenerator$4.accept(InvokerBytecodeGenerator.java:558) at java.base/java.lang.invoke.InvokerBytecodeGenerator$4.accept(InvokerBytecodeGenerator.java:555) at java.base/java.lang.invoke.InvokerBytecodeGenerator$2.accept(InvokerBytecodeGenerator.java:282) at java.base/java.lang.invoke.InvokerBytecodeGenerator$2.accept(InvokerBytecodeGenerator.java:276) at java.base/jdk.internal.classfile.impl.ClassFileImpl.build(ClassFileImpl.java:113) at java.base/java.lang.classfile.ClassFile.build(ClassFile.java:332) at java.base/java.lang.invoke.InvokerBytecodeGenerator.classFileSetup(InvokerBytecodeGenerator.java:276) at java.base/java.lang.invoke.InvokerBytecodeGenerator.generateCustomizedCodeBytes(InvokerBytecodeGenerator.java:555) at java.base/java.lang.invoke.InvokerBytecodeGenerator.generateCustomizedCode(InvokerBytecodeGenerator.java:533) at java.base/java.lang.invoke.LambdaForm.compileToBytecode(LambdaForm.java:845) at java.base/java.lang.invoke.DirectMethodHandle.makePreparedLambdaForm(DirectMethodHandle.java:302) at java.base/java.lang.invoke.DirectMethodHandle.preparedLambdaForm(DirectMethodHandle.java:230) at java.base/java.lang.invoke.DirectMethodHandle.preparedLambdaForm(DirectMethodHandle.java:215) at java.base/java.lang.invoke.DirectMethodHandle.preparedLambdaForm(DirectMethodHandle.java:224) at java.base/java.lang.invoke.DirectMethodHandle.make(DirectMethodHandle.java:106) at java.base/java.lang.invoke.MethodHandles$Lookup.getDirectMethodCommon(MethodHandles.java:4109) at java.base/java.lang.invoke.MethodHandles$Lookup.getDirectMethodNoSecurityManager(MethodHandles.java:4065) at java.base/java.lang.invoke.MethodHandles$Lookup.getDirectMethodForConstant(MethodHandles.java:4314) at java.base/java.lang.invoke.MethodHandles$Lookup.linkMethodHandleConstant(MethodHandles.java:4262) at java.base/java.lang.invoke.MethodHandleNatives.linkMethodHandleConstant(MethodHandleNatives.java:628) at java.base/jdk.internal.module.SystemModuleFinders$1.find(SystemModuleFinders.java:216) at java.base/jdk.internal.module.ModuleBootstrap.boot2(ModuleBootstrap.java:260) at java.base/jdk.internal.module.ModuleBootstrap.boot(ModuleBootstrap.java:173) at java.base/java.lang.System.initPhase2(System.java:2312) ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20611#discussion_r1721082199
