search

JDKMissionControl / jmc

This mirror is deprecated - please start using https://github.com/openjdk/jmc
197 stars 46 forks source link

Memory pressure and bytes no longer available #6

Open ghost opened 5 years ago

ghost commented 5 years ago

I was using jmc on Java 8 to find and reduce allocations by looking at the memory pressure for different call stacsk, which was correlated with allocations sizes (not object counts).

I'm now using the early access jmc, which I built, for Java 11. It appears that the memory pressure and allocation size is no longer available per call stack. There is only object count per call stack, which I believe is not correlated to GC pressure, or at least not as directly as allocation sizes.

Is there any plan to add back the pressure and size columns, and to be able to sort the call stacks by these values? If not I will have to evaluate other options for profiling, so I would very much appreciate a response, even if the answer is incomplete at this time.

thegreystone commented 5 years ago

Hi there!

The short answer is yes. Here is the already opened ticket: https://bugs.openjdk.java.net/browse/JMC-5923

JMC 7 is closed for development at this point, but this will hopefully get done in time for JMC 7.1.

The slightly longer answer is that there are currently a lot of other fish to fry, first one being figuring out how to finally get JMC 7 out the door. If you're a Java developer, and you like what we're doing over here, we're always grateful for help and contributions! :)

ghost commented 5 years ago

@thegreystone thank you very much for the quick reply! I should have searched the openjdk issues first, sorry about that. I'm very glad to know it will be coming in 7.1.

thegreystone commented 5 years ago

Also, even though this is not exactly what you're looking for, you have the Memory page, which really gives you the estimated "allocation pressure" (i.e. Total Allocation) per class. You can use it together with, e.g., the TLAB allocation page and the "Store and Set as Focused Selection", or even the Stacktrace view, to see the "Allocation Pressure" from various angles.