We were discussing garbage collection and compaction.With objects, we don't have to create the graph. Instead we have to find ways to classify them by generation. Any classification of the objects is considered temporary until the next usage. At that point, the same objects may need reclassification. Since the classification is temporal, we run the risk of mislabeling generations and consequently reclaiming an object when it wasn't supposed to be.
We can also consider a markdown approach where after labeling the objects, we progressively mark them down so that we take actions only on the labels that are older than the oldest classification. This will help with keeping the classification and the reaping separate. The above approach will enable no actions to be taken if just the classification is needed. And also helping with taking different actions on the different tiers. For example, evict and delete may be considered separate actions.
The unit of moving operation is an object here only because applications use objects. However, the cache may choose to stash swaths of objects at a time for shifting or ignoring. For example, we could use heap to keep track of the biggest available swath to roll for objects of arbitrary size.
We may also have a compact version for keeping a running track of all the swaths. For example, if they are consecutive, we could coalesce them. If there is a set of active objects that can be margined into a swath, it can be marked as busy and ignored. If there are too many alternating swaths of free and busy object swaths, they can be retained as such and ignored from coalescing.
Busy swaths may need to be updated as candidate for conversion to free whenever objects are moved out of it.
Busy swaths can also be coalesced if they permit. This is usually not necessary because it is too aggressive and only a tiny fraction of the overall collection.
Movements of free and busy swaths are always opposite to each other. The free swaths move towards the younger generation where they can be utilized for gen 0.
The movement operation itself can be optimized by efficient bookkeeping so that it translates only to updates in the book-keeping
We can also consider a markdown approach where after labeling the objects, we progressively mark them down so that we take actions only on the labels that are older than the oldest classification. This will help with keeping the classification and the reaping separate. The above approach will enable no actions to be taken if just the classification is needed. And also helping with taking different actions on the different tiers. For example, evict and delete may be considered separate actions.
The unit of moving operation is an object here only because applications use objects. However, the cache may choose to stash swaths of objects at a time for shifting or ignoring. For example, we could use heap to keep track of the biggest available swath to roll for objects of arbitrary size.
We may also have a compact version for keeping a running track of all the swaths. For example, if they are consecutive, we could coalesce them. If there is a set of active objects that can be margined into a swath, it can be marked as busy and ignored. If there are too many alternating swaths of free and busy object swaths, they can be retained as such and ignored from coalescing.
Busy swaths may need to be updated as candidate for conversion to free whenever objects are moved out of it.
Busy swaths can also be coalesced if they permit. This is usually not necessary because it is too aggressive and only a tiny fraction of the overall collection.
Movements of free and busy swaths are always opposite to each other. The free swaths move towards the younger generation where they can be utilized for gen 0.
The movement operation itself can be optimized by efficient bookkeeping so that it translates only to updates in the book-keeping
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