Playing-with-jvm

Repository where I experiment with JVM internal such as JIT and various performance optimizations techniques.

How to run

To run a particular benchmark:

jmh:run  .*IncWhile.*

or you can run all benchmarks at once

jmh:run

You can also overload benchmark settings with provided parameters to command line

jmh:run -i 3 -wi 3 -f1 -t1 .*IncWhile.*

JVM options worth checking before starting experiments

Following list I found useful during experiments with JVM. Details can be found in Java SE Tools Reference

• -XX:+PrintCompilation - Prints a message when method is compiled
• -XX:+UnlockDiagnosticVMOptions - option that unlocks diagnostic JVM options which are not collected during runtime otherwise
• -XX:+PrintAssembly - prints assembly code for bytecode and native methods
• -XX:+LogCompilation - logs compilation activity to a file
• -XX:+TraceClassLoading - trace a class as they are loaded
• -verbose:gc - displays information about each GC event
• -verbose:class - displays information about each class loaded
• -XX:+PrintInlining - prints inlining decesions
• -XX:-Inline - disables method inlining
• -XX:CompileCommand - specifies a command to perform on a method, e.g.

-XX:CompileCommand=dontinline, com/jaksky/jvm/tests/jit/IncFor.inc

prevents inlining of com.jaksky.jvm.tests.jit.IncFor.inc method