On Mon, 26 Jun 2023 21:56:21 GMT, David Holmes <dhol...@openjdk.org> wrote:

> I would think it is likely to fail with OOME under the same GC stress test 
> conditions.
> 
> But if this is just a stress test issue then bailing out when the loading 
> fails would be far simpler than pre-loading the class. You've added to the VM 
> startup cost just to avoid a stress test failure.

Any app running near the GC limit can cause this and we've seen this with 
libgraal in practice. When the VM is near the GC limit, any compilation can 
cause an OOME and then when that OOME wants to be translated back to libgraal, 
it can be the first time VMSupport is used.
The time for loading `VMSupport` eagerly is in the noise.
For example, `-verbose:class` shows that about 30 classes (including 
`VMSupport`) are loaded in 1ms:

[0.011s][info][class,load] java.lang.reflect.Executable source: shared objects 
file
[0.012s][info][class,load] java.lang.reflect.Method source: shared objects file
[0.012s][info][class,load] java.lang.reflect.Constructor source: shared objects 
file
[0.012s][info][class,load] jdk.internal.vm.ContinuationScope source: shared 
objects file
[0.012s][info][class,load] jdk.internal.vm.Continuation source: shared objects 
file
[0.012s][info][class,load] jdk.internal.vm.StackChunk source: shared objects 
file
[0.012s][info][class,load] jdk.internal.vm.VMSupport source: shared objects file
[0.012s][info][class,load] jdk.internal.reflect.MagicAccessorImpl source: 
shared objects file
[0.012s][info][class,load] jdk.internal.reflect.MethodAccessor source: shared 
objects file
[0.012s][info][class,load] jdk.internal.reflect.MethodAccessorImpl source: 
shared objects file
[0.012s][info][class,load] jdk.internal.reflect.DelegatingClassLoader source: 
shared objects file
[0.012s][info][class,load] jdk.internal.reflect.ConstantPool source: shared 
objects file
[0.012s][info][class,load] java.lang.annotation.Annotation source: shared 
objects file
[0.012s][info][class,load] jdk.internal.reflect.CallerSensitive source: shared 
objects file
[0.012s][info][class,load] jdk.internal.reflect.ConstructorAccessor source: 
shared objects file
[0.012s][info][class,load] jdk.internal.reflect.ConstructorAccessorImpl source: 
shared objects file
[0.012s][info][class,load] 
jdk.internal.reflect.DirectConstructorHandleAccessor$NativeAccessor source: 
shared objects file
[0.012s][info][class,load] 
jdk.internal.reflect.SerializationConstructorAccessorImpl source: shared 
objects file
[0.012s][info][class,load] java.lang.invoke.MethodHandle source: shared objects 
file
[0.012s][info][class,load] java.lang.invoke.DirectMethodHandle source: shared 
objects file
[0.012s][info][class,load] java.lang.invoke.VarHandle source: shared objects 
file
[0.012s][info][class,load] java.lang.invoke.MemberName source: shared objects 
file
[0.012s][info][class,load] java.lang.invoke.ResolvedMethodName source: shared 
objects file
[0.012s][info][class,load] java.lang.invoke.MethodHandleNatives source: shared 
objects file
[0.012s][info][class,load] java.lang.invoke.LambdaForm source: shared objects 
file
[0.012s][info][class,load] java.lang.invoke.TypeDescriptor$OfMethod source: 
shared objects file
[0.012s][info][class,load] java.lang.invoke.MethodType source: shared objects 
file
[0.012s][info][class,load] java.lang.BootstrapMethodError source: shared 
objects file
[0.012s][info][class,load] java.lang.invoke.CallSite source: shared objects file
[0.012s][info][class,load] jdk.internal.foreign.abi.NativeEntryPoint source: 
shared objects file
[0.012s][info][class,load] jdk.internal.foreign.abi.ABIDescriptor source: 
shared objects file
[0.012s][info][class,load] jdk.internal.foreign.abi.VMStorage source: shared 
objects file
[0.013s][info][class,load] jdk.internal.foreign.abi.UpcallLinker$CallRegs 
source: shared objects file

-------------

PR Comment: https://git.openjdk.org/jdk/pull/14641#issuecomment-1608388679

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