JMH 1.21

[Aleksey Shipilev]

Hi,

JMH 1.21 is released and available at Maven Central. This is a maintenance release, it is focuses on
improving OpenJDK-derived JVMs support.

 *) Compiler hits detection fixed for GraalVM (critical for correctness!):
   https://bugs.openjdk.java.net/browse/CODETOOLS-7902164

 *) Runner now prints warning messages about unsupported and experimentally supported VMs:
   https://bugs.openjdk.java.net/browse/CODETOOLS-7902168

   Note: experimental support means you need to be extra careful during experiments. Submit bug
reports to either VM developers or here, if you find something peculiar. For example, we know at
least two minor issues that affect GraalVM today:
   https://github.com/oracle/graal/issues/397
   https://github.com/oracle/graal/issues/402

 *) Defaults for warmup/measurement/forks were reconsidered to allow longer in-JVM runs. This is
important for the VMs/benchmarks where time-to-performance is substantial. Instead of 20x1s warmup,
20x1s measurement, 10 forks, we are now doing 5x10s warmup, 5x10s measurement, 5 forks. It increases
the default time for around 1.25x, and single fork has 2.5x more time to warmup and complete.
   https://bugs.openjdk.java.net/browse/CODETOOLS-7902170
   https://bugs.openjdk.java.net/browse/CODETOOLS-7902165

 *) Runner now captures and prints the VM name, in case it is not "OpenJDK":
   https://bugs.openjdk.java.net/browse/CODETOOLS-7902169

 *) Runner now prints the paragraph about trusting the numbers at the end of the run:
   https://bugs.openjdk.java.net/browse/CODETOOLS-7902167

Enjoy!
-Aleksey