Memory allocation tracking

[will.sargent]

Hi there,

I'm interested in seeing what improvements there are in the JVM from 1.8 to 11. Running Yourkit, I can see that in 1.8 with the same application code the allocation rate is 2.6 M/sec, and running with JDK 11, it's only 350 K/sec. I'd like to find out what the difference is between JVMs, but when I turn on full memory allocation sampling, the allocation rate jumps from 350K to 900K, so something in the profiling disables some optimizations.

Here's the blog post with more details:

https://tersesystems.com/blog/2020/08/2 ... th-jdk-14/

and the application results:

https://github.com/wsargent/memalloctes ... er/results

is there a way to find what is causing the delta between JVMs?

[Anton Katilin]

Hello,

Exactly what object allocation mode did you use? If you are interested in the rate, I think the best option is object counting ("Count allocated objects" in the UI, startup option "alloc_object_counting" - see https://www.yourkit.com/docs/java/help/allocations.jsp ).

Also, could you please try to specify the startup option "disable_heap_sampling" when running on Java 11+. Does the rate change?

How to specify: https://www.yourkit.com/docs/java/help/ ... ptions.jsp

Best regards,
Anton

[Anton Katilin]

Update:

If you are interested in the rate, I think the best option is object counting

Perhaps even better mode for your purpose is the "Record thread and stack" mode with sampled stacks and very large size limit and record-each value e.g. 10000000 both. This should reduce object creation callback workload and hence the allocation recording overhead to minimum. Please note that the size limit and record-each parameters do not affect the object creation rate shown in the telemetry, it always accounts all created objects.

The suggestion to try "disable_heap_sampling" for Java 11+ is still relevant.