[12] RFR(S) 8209165: [GRAAL] Skip Graal build if C1 is not present

[Vladimir Kozlov]

Yes, you can do that to avoid missing C1 issue with Graal. But it is "too complicated" for end user ;)
User have to generate these libraries himself. On other hand we are planning to ship libgraal.so with JDK.

And with this you solve only startup problem. Even that is questionable based on our experiments. If AOT library is big 
(like when you compile whole module), its load time and symbols resolution offsets benefit of pre-compilation.

Also produced like that AOT code is just extension from existing code in CodeCache. It still shares Java heap with 
application during compilation and have other side effects. It could be deoptimized as you noticed and go into 
Interpreter polluting profiling again. It happens because we make very conservative assumptions during AOT compilation.

Yes, there are different ways to solve GRaal's issues and we decided to go with libgraal.so as we think it will solve 
most of these issues.

Regards,
Vladimir

On 8/10/18 9:22 AM, Liu Xin wrote:
> Vladimir,
> 
> I am quite new area.  Why Graal needs its own GC and small runtime?  Theoretically, jaotc compiles some Java classes. It doesn’t need to know that those classes are themselves.
> My original thought is straight-forward. Compile Graal classes using JOT, load them to avoid from warming-up.
> 
> I compiled both modules:
>   ./jdk/bin/jaotc --module jdk.internal.vm.ci --output libHotspotCI.dylib
>   ./jdk/bin/jaotc --module jdk.internal.vm.compiler --output libHotspotCompiler.dylib
> 
> And I loaded them to run.
> ./jdk/bin/java -XX:+PrintCompilation \
>       -XX:+UnlockExperimentalVMOptions \
>       -XX:+EnableJVMCI \
>       -XX:+UseJVMCICompiler  -XX:AOTLibrary=./libHotspotCI.dylib:./libHotSpotCompiler.dylib  -cp .  Demo |& tee jvmci_with_aot_graal.output
> 
> Does it work? I took a look the output of PrintCompilation.
> I found many methods are marked 'made not entrant’.   It means that hotspot deoptimize them right?
> 
> 
>> On Aug 9, 2018, at 11:26 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>>
>>
>> My main motivation is that it is not supported configuration for us. And if you don't use Graal you waste space with Graal module.
>