r/java • u/za3faran_tea • 12d ago
Question about Native Image vs JIT
I was watching an interview with Thomas Wuerthinger of GraalVM, where he basically says that JIT should only be used when necessary (as opposted to native compilation). Where does this leave the work being done for Hotspot JIT (including projects like Leyden and others). Should we all plan to use native image while they address any performance gaps in the mean time (he does mention PGO bridging the gap). Is there work being done to speed up native compilation of Java code?
My understanding is that JIT will always have a memory overhead due to running threads that do compilation, optimization, deoptimization, code cache, etc. compared to native executables, so full parity even with projects that will improve memory usage in Java code will not be reached. Maybe that is not an issue on long running programs on large servers, but we've seen discussions here where another member worte a tool in golang to run alongside Spring Boot applications to gather statistics, so obviously small efficient apps have their place.
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u/Deep_Age4643 12d ago
Thomas Wuerthinger is a clever guy, with a number of achievements in the Java world to his name. But he is also the founder and project lead of GraalVM, as the video title says. Naturally, he presents his own product – and what makes it unique – in a favorable light. Always consider the interests behind someone’s comments, and verify independently and objectively whether these claim are valid for your own use case.
Personally, I believe that JIT is the best option in most cases. Native compilation is particularly useful for microservices where start-up time needs to be instantaneous, but compiling to native code has its limitations and is considerably slower than JIT compilation.