JEP 515: Ahead-of-Time Method Profiling

JEP 515: Ahead-of-Time Method Profilingopenjdk.org

Now also hotspot optimisation can be cached. RUN :

scripts/jep515/method-profiling.sh

It uses aot method profiling for sample file directly taken from JEP site. Measurements :

---- Total time without AOT cache ----
real 0.11
user 0.21
sys 0.07

---- Total time with AOT cache ----
real 0.10
user 0.18
sys 0.08

JEP 515 extends the AOT cache so it can store method-execution profiles, not only class loading and linking metadata. In this example, the second run with the AOT cache is slightly faster overall (real 0.11 -> 0.10) and spends less CPU time in user mode (user 0.21 -> 0.18). This means the JVM had to do less profiling and warm-up work during startup and early execution, because it could reuse profile information collected during the training run. The important point is that JEP 515 is not mainly about faster class loading; it is about helping the JIT compiler make good optimization decisions earlier, so the application reaches peak performance sooner.