Thanks Andreas. I guess I should have explained my situation. Basically, what I was trying to do (and I did at the end) is to use the last free bit of the object header to use it to detect used and unused objects. I modified the VM so that when an object receives a message, it enables such bit. I also have primitives to mark and unmark all objects.

I am not sure what I will do then with the unused objects, but for the moment, I just wanted to get numbers. Statistics. So, for example I wanted to know how many objects were with the bit on and how many with the bit off. Also the amount of memory those objects represents.

The method is:

primitiveGetStadistics
��� | oop usedCount unusedCount results usedMemory unusedMemory usedCountOop unusedCountOop usedMemoryOop unusedMemoryOop |
���
��� usedCount := unusedCount := 0.
��� usedMemory := unusedMemory := 0.
���
��� self print: 'Start to check objects'; cr.
��� oop := self firstAccessibleObject.
��� [oop = nil] whileFalse: [
��� ��� (self isIntegerObject:� oop)
��� ��� ��� ifFalse: [
��� ��� ��� ��� (self internalIsUsed: oop)
��� ��� ��� ��� ��� ifTrue: [
��� ��� ��� ��� ��� ��� usedCount := usedCount +1.
��� ��� ��� ��� ��� ��� usedMemory := usedMemory + (self internalByteSize: oop). ]
��� ��� ��� ��� ��� ifFalse: [
��� ��� ��� ��� ��� ��� unusedCount := unusedCount +1.
��� ��� ��� ��� ��� ��� unusedMemory := unusedMemory + (self internalByteSize: oop). ].
��� ��� ��� ].
��� ��� oop := self accessibleObjectAfter: oop.
��� ].
��� self print: 'Finish to check objects'; cr.
���
��� self print: 'Push stadistics'; cr.
��� self pushRemappableOop:
��� ��� (self instantiateClass: (self classArray) indexableSize: 4).
��� self pushRemappableOop:
��� ��� (self positive64BitIntegerFor: usedCount).
��� self pushRemappableOop:
��� ��� (self positive64BitIntegerFor: usedMemory).
��� self pushRemappableOop:
��� ��� (self positive64BitIntegerFor: unusedCount).
��� self pushRemappableOop:
��� ��� (self positive64BitIntegerFor: unusedMemory).
���
��� self print: 'Pop stadistics'; cr.
��� unusedMemoryOop := self popRemappableOop.
��� unusedCountOop := self popRemappableOop.
��� usedMemoryOop := self popRemappableOop.
��� usedCountOop := self popRemappableOop.
��� results := self popRemappableOop.���
��� ���
��� self print: 'Write stadistics in array'; cr.
��� self storePointer: 0 ofObject: results withValue: usedCountOop.
��� self storePointer: 1 ofObject: results withValue: unusedCountOop.
��� self storePointer: 2 ofObject: results withValue: usedMemoryOop.
��� self storePointer: 3 ofObject: results withValue: unusedMemoryOop.
���
��� self print: 'Push result array in stadistics'; cr.
��� self pop: 1 thenPush: results.
���
���


And as you may guess,
internalIsUsed: oop
��� self inline: true.
��� ^((self baseHeader: oop) bitAnd: UsedObjectBit) ~= 0


So then, from the image side, I can get statistics at certain point, and get something like the attached screenshot.

Thanks.

Mariano

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