VisualVM starting profiler causes memory usage to drop?

Question

As seen in the Monitor for memory diagram (https://i.stack.imgur.com/sBKzO.png), around 4:35PM is when I started VisualVM Profiler and it caused memory usage to drop by ~7G which is quite significant. Why did this happen? It is as if starting the profiler allowed many more memory objects to be reclaimed -- but why weren't they garbage collected in the many GC rounds before that?

(Around 4:49 is when I clicked "Snapshot" in Profiler and there was a similar drop but to a lesser extent.)

I am quite confused and would greatly appreciate if anyone can shed some light on this behavior. Thanks!

Attaching a profiler can cause more full GCs to be triggered, that would reduce the memory used briefly. — Peter Lawrey, Jun 20 '11 at 17:36
Ahh that makes sense, I think that is indeed what's happening here, thanks a lot Peter! — welkin, Jun 21 '11 at 15:13

score 0 · Accepted Answer · answered Jun 21 '11 at 15:15

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Attaching a profiler can cause more full GCs to be triggered, that would reduce the memory used briefly.

answered Jun 21 '11 at 15:15

Peter Lawrey

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VisualVM starting profiler causes memory usage to drop?

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