[Vm-dev] Garbage collector issue
bert at freudenbergs.de
Thu Jan 26 14:28:08 UTC 2017
What exactly is the behavior in Pharo?
In a recent Squeak on Spur I don't see anything unusual. In my image there
are 9 Object instances. Then I added the "Object basicNew" in
#checkForNewScreenSize and the instance count of Object starts increasing
rapidly until the next incremental GC, which happens about every 10
seconds, then the count drops and starts increasing again.
I verified it like this:
(UpdatingStringMorph on: Object selector: #instanceCount) openInHand
... which continuously shows the number of instances, and
(UpdatingStringMorph on: [Smalltalk vmParameterAt: 9] selector: #value)
... which shows the number of incremental GCs.
Is it possible that in your image there is so little garbage generated that
no incremental GC is triggered for a long time? My image has dozens of
windows and stepping morphs. I'd try to log vm param 9 along with your inst
- Bert -
On Thu, Jan 26, 2017 at 2:58 PM, Pavel Krivanek <pavel.krivanek at gmail.com>
> Strange, in Pharo 3 it behaves the same way. So probably not directly Spur
> -- Pavel
> 2017-01-26 14:52 GMT+01:00 Clément Bera <bera.clement at gmail.com>:
>> Is it the same behavior in Pharo 3 ?
>> Just wondering if this is a Spur issue or if it is non related to Spur.
>> On Thu, Jan 26, 2017 at 2:38 PM, Pavel Krivanek <pavel.krivanek at gmail.com
>> > wrote:
>>> in Pharo and in Squeak, if you try to print:
>>> Point allInstances size.
>>> several times, you will get fastly growing number of Point instances in
>>> most cases. But when you do:
>>> Smalltalk garbageCollect. Point allInstances size.
>>> The number of instances is quite stable.
>>> I realized that about every 5 milliseconds two new Point instances are
>>> created and not collected in reasonable time. I tried to find what points
>>> to them and I realized that nothing. That two instances contain display
>>> size so it was easy to find the place where these points are created. In
>>> Pharo it is in
>>> "Check whether the screen size has changed and if so take appropriate
>>> Display extent = DisplayScreen actualScreenSize ifTrue: [^ Display].
>>> DisplayScreen startUp.
>>> World restoreMorphicDisplay.
>>> As you can see in the code, the two point instances are only very
>>> temporary objects. And with some experiments I realized that that behavior
>>> is not Point specific (eg. some problem with the @ primitive). Because if
>>> you replace the code of the method with only Object basicNew, the growth of
>>> Object instances is similar. See the attached script.
>>> pharo-ui Pharo st script2.st
>>> -- Pavel
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