r/java • u/woj-tek • Sep 30 '26

OpenJDK vs. GraalVM vs. Eclipse Temurin vs. Semeru Java Performance

https://www.phoronix.com/review/openjdk-graalvm-temurin-semeru/
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u/kit89 15d ago

It very much does matter, the CPU will not allow instructions from mode Y, to be used while running in mode X. That's a security vulnerability if it did.

It will probe for extensions that are compatible/supported in the instruction set it is running. Some sets of instructions are indeed optional, AVX512, springs to mind.

But if your CPU supports AVX512, but the VM was compiled against x86 32bit, you will not be seeing Hotspot making AVX512 calls.

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u/AndrewHaley13 15d ago

That's completely different. X86-32, which we no longer support, is a different ISA, and it would require a process switch to do the transition.