Wednesday, September 27, 2017
If you're reading this, I hope you're curious what your options are when it comes to running JVM diagnostic tools on containerized applications. Generally when it comes to containers, you can either shove all your diagnostic tools into the container image, or you can try running them from the host -- this short post tries to explain what works, what doesn't, and what can be done about it. Although it is focused on JVM tools (and HotSpot specifically), a lot of the same obstacles will apply to other runtimes and languages.
As a very quick reminder, container isolation on...
Friday, July 7, 2017
I hope you're outraged that your performance tools are lying to you. For quite a while, many Java sampling profilers have been known to blatantly misrepresent reality. In a nutshell, stack sampling using the documented JVMTI GetStackTrace method produces results that are biased towards safepoints, and not representative of the real CPU processing performed by your program.
Over the years, alternative profilers popped up, trying to fix this problem by using AsyncGetCallTrace, a less-documented API that doesn't wait for a safepoint, and can produce more accurate results. Simply calling AGCT from a timer signal handler gives you a fairly reliable way...