Getting Dtraceasm profiler to work with JMH on macOS

[Patrick Concannon]

Hi,

It seems the Dtraceasm profiler does not work with JMH on macOS, and a 
couple of hacks are needed in order to get it working consistently. I 
spoke to Paul Sandoz about this issue, and he was able to provide me 
with the workaround described below.

When using dtraceasm, a dtrace process is executed that samples the 
program counter of processes, and the sampling results are then streamed 
to a file.  The first issue is that the output file is not getting 
updated with samples when JMH kills the dtrace process.
Paul provided the small patch (below) that explicitly sends a signal to 
the sudo process to make sure dtrace spits out the required results.  He 
mentioned that this might be something to do with the Java 
implementation of Process.destroy.


diff -r 1a48e97d9dea 
jmh-core/src/main/java/org/openjdk/jmh/profile/DTraceAsmProfiler.java
--- 
a/jmh-core/src/main/java/org/openjdk/jmh/profile/DTraceAsmProfiler.java 
Fri Feb 14 09:42:04 2020 +0100
+++ 
b/jmh-core/src/main/java/org/openjdk/jmh/profile/DTraceAsmProfiler.java 
Mon Feb 24 12:20:48 2020 -0800
@@ -87,6 +87,9 @@
              throw new IllegalStateException("DTrace needs the forked 
VM PID, but it is not initialized");
          }
+        long dtracePid = dtraceProcess.pid();
+        Utils.tryWith("sudo", "kill", "-15", Long.toString(dtracePid));
+
          Collection<String> messages = Utils.destroy(dtraceProcess);
          if (!messages.isEmpty()) {
              throw new IllegalStateException(messages.toString());


As well as applying the patch above, you also have to ensure the hsdis 
library is preloaded when running the JVM. The easiest way to ensure 
this is to place it in the current directory. This avoids the pain of 
breaking out of the mac sandbox for preloading libraries. This issue was 
previously discussed here: 
http://mail.openjdk.java.net/pipermail/jmh-dev/2018-January/002686.html.


While the solution above works, it is not ideal. I wanted to send this 
email to the list to see if there was any interest in possibly finding a 
more permanent solution to this?


Kind regards,

Patrick