test for memory leaks (brand=phet-io)

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For instrumented sims, memory leak testing must be done separately for the phet-io brand, because according to the How to Instrument document:

Perform a full test for memory leaks. The benchmark dev release can be helpful here. This will help catch faulty tandem disposal. PhET-iO instantiates different objects and wires up listeners that are not present in the PhET-branded simulation. It needs to be tested separately for memory leaks.

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Slack dev-public:

Sam Reid [9:56 AM]
Memory leak testing Graphing Quadratics PhET-iO over the last 5 minutes doesn’t suggest any serious memory leaks (it’s just the normal slow rising pattern). I also don’t see any tandems being added after the sim starts up, so that’s a good indicator that there are no phet-io related memory leaks.

Chris Malley [9:59 AM]
Thanks, that matches what I see. I wasn’t aware of this “normal slow rising pattern”. When I tested Equality Explorer (5 screens), it started at 71MB and then oscillated around 82MB.

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#14 (review of PhET-iO instrumentation) is a prerequisite to doing memory leak testing.

[samreid]

The main part of the work in #14 is complete, removing "block" status. @chrisklus are running a 10-minute memory test for this. Initial heap size (after about a minute) is 73.6MB. We'll report back in 10 minutes with the second snapshot. Keep in mind that phetsims/unit-rates#207 may be related to this memory issue.

UPDATE: After 10 minutes, the memory is at 77.7MB:

@chrisklus and I will briefly review the deltas, but in my opinion, this is either (a) an acceptably low memory leak for publication or (b) not a memory leak at all, just the natural memory expansion during initial use.

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Why are you doing a memory leak test before all PhET-iO related issues have been addressed? And did someone ask you to self-assign?

[samreid]

Everything seems OK for now, we can run another test after checking off all other PhET-iO issues. Putting on hold until all other phet-io issues have been addressed.

UPDATE: I provided a more thorough answer on slack:

We are checking through status of Graphing Quadratics and PhET-iO blocking issues, and wanted to do an intermediate test of memory. We’ll be continuing on Graphing Quadratics/PhET-iO until at least noon.

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For comparison, the latest brand=phet memory tests are in #106 (~41MB startup, ~52MB stable).

Test results for brand=phet-io:

• 1.0.0-dev.46 with ?standalone&fuzz
• Chrome 70.0.3538.102
• macOS 10.11.6 on MacBook Pro

Minutes	Heap Size (MB)
0	43.9
5	52.2
10	53.6
15	54.6
20	54.7
25	55.4
30	55.5
45	55.6

This looks fine. PhET-iO appears to add < 4MB of overhead to brand=phet, and that seems reasonable. Closing.