[master] RFR: 8264311: Heap object statistics

Aleksey Shipilev shade at openjdk.java.net
Wed May 5 14:24:24 UTC 2021

On Wed, 5 May 2021 14:17:34 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> For Lilliput evaluation, it would be useful to be able to get some statistics about heap objects, e.g. how many objects there typically are, what is their (average) size, how big is the live data set, how many objecs have an identity hash code and how many objects are locked. Some of that information may be useful for general purpose too, e.g. the avg live data set and object size/count information might be quite useful to have.
> Heap object statistics can be gathered and printed by invoking java with -XX:+UnlockDiagnosticVMOptions -XX:+HeapObjectStats -Xlog:heap+stats. It will impact performance of the workload. The sampling interval can be specificed by -XX:HeapObjectStatsSamplingInterval=X (in ms) and defaults to 500 (ms).
> Testing:
>  - [x] Some manual tests, verifying the plausability of the output by hand
>  - [x] tier1
>  - [x] tier2

Marked as reviewed by shade (Committer).

src/hotspot/share/services/heapObjectStatistics.hpp line 43:

> 41: class HeapObjectStatistics : public CHeapObj<mtGC> {
> 42: private:
> 43:   static const int HISTOGRAM_SIZE = 16;

This fields looks unused.


PR: https://git.openjdk.java.net/lilliput/pull/1

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