Excessive locking in TypeCachingBytecodeGenerator#BOOTSTRAP_LOCK

[aswath80]

The TypeCachingBytecodeGenerator#BOOTSTRAP_LOCK is resulting in excessive BLOCKED threads when running several thousand tests concurrently. Byte-buddy TypeCache's findOrInsert without monitor seems to handle concurrency. Is this global lock needed ?

Mockito-Inline 4.10, Byte-Buddy 1.12.19

"ForkJoinPool-1-worker-84" Id=115 RUNNABLE (daemon=TRUE) at java.base@17.0.4/java.lang.StringLatin1.replace(StringLatin1.java:322) at java.base@17.0.4/java.lang.String.replace(String.java:2806) at app//net.bytebuddy.jar.asm.Type.getInternalName(Type.java:510) at app//net.bytebuddy.jar.asm.Type.appendDescriptor(Type.java:644) at app//net.bytebuddy.jar.asm.Type.getMethodDescriptor(Type.java:585) at app//net.bytebuddy.description.method.MethodDescription$ForLoadedMethod.getDescriptor(MethodDescription.java:1288) at app//net.bytebuddy.asm.Advice$Dispatcher$Inlining$Resolved$AdviceMethodInliner.visitMethod(Advice.java:8400) at app//net.bytebuddy.jar.asm.ClassReader.readMethod(ClassReader.java:1353) at app//net.bytebuddy.jar.asm.ClassReader.accept(ClassReader.java:744) at app//net.bytebuddy.jar.asm.ClassReader.accept(ClassReader.java:424) at app//net.bytebuddy.asm.Advice$Dispatcher$Inlining$Resolved$AdviceMethodInliner.apply(Advice.java:8394) at app//net.bytebuddy.asm.Advice$AdviceVisitor$WithExitAdvice.onUserEnd(Advice.java:10904) at app//net.bytebuddy.asm.Advice$AdviceVisitor.visitMaxs(Advice.java:10683) at app//net.bytebuddy.jar.asm.ClassReader.readCode(ClassReader.java:2665) at app//net.bytebuddy.jar.asm.ClassReader.readMethod(ClassReader.java:1514) at app//net.bytebuddy.jar.asm.ClassReader.accept(ClassReader.java:744) at app//net.bytebuddy.jar.asm.ClassReader.accept(ClassReader.java:424) at app//net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForInlining.create(TypeWriter.java:4014) at app//net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:2224) at app//net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$UsingTypeWriter.make(DynamicType.java:4050) at app//net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:3734) at app//org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.transform(InlineBytecodeGenerator.java:401) at java.instrument@17.0.4/java.lang.instrument.ClassFileTransformer.transform(ClassFileTransformer.java:244) at java.instrument@17.0.4/sun.instrument.TransformerManager.transform(TransformerManager.java:188) at java.instrument@17.0.4/sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:541) at java.instrument@17.0.4/sun.instrument.InstrumentationImpl.retransformClasses0(Native Method) at java.instrument@17.0.4/sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:169) at app//org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.triggerRetransformation(InlineBytecodeGenerator.java:280) at app//org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.mockClass(InlineBytecodeGenerator.java:217) - locked <0x730e33e8> (a org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator) at app//org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.lambda$mockClass$0(TypeCachingBytecodeGenerator.java:47) at app//org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$$Lambda$895/0x0000000801aeaf98.call(Unknown Source) at app//net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:168) at app//net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:399) at app//net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:190) - locked <0x62f72614> (a java.lang.Object) at app//net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:410)

"ForkJoinPool-1-worker-51" Id=82 BLOCKED on java.lang.Object@62f72614 owned by "ForkJoinPool-1-worker-84" Id=115115 (daemon=TRUE) at app//net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:189) at app//net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:410) at app//org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.mockClass(TypeCachingBytecodeGenerator.java:40) at app//org.mockito.internal.creation.bytebuddy.InlineDelegateByteBuddyMockMaker.createMockType(InlineDelegateByteBuddyMockMaker.java:396) at app//org.mockito.internal.creation.bytebuddy.InlineDelegateByteBuddyMockMaker.doCreateMock(InlineDelegateByteBuddyMockMaker.java:355) at app//org.mockito.internal.creation.bytebuddy.InlineDelegateByteBuddyMockMaker.createMock(InlineDelegateByteBuddyMockMaker.java:334) at app//org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker.createMock(InlineByteBuddyMockMaker.java:56) at app//org.mockito.internal.util.MockUtil.createMock(MockUtil.java:99)

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[AndreasTu]

I have opened the PR #3095, which would ease this issue, by changing the locking scheme in TypeCachingBytecodeGenerator from a single global lock to cacheLocks with size 16.
The used TypeCachingLock from cacheLocks depends on the hashcode of MockitoMockKey, which aggregates the types and
settings to mock.

So this will spread the Locks over 16 instances, assuming that the hashcodes of the class to mock are more or less evenly distributed.