I am experimenting with Weak.Make to increase sharing of strings. It works as expected that values in a weak set disappear when they are no longer referenced otherwise. But inspecting the memory of the weak set it does not seem to change. The code below adds strings to a weak hash set, removes refe…

My guess would be that Obj.reachable_words is returning the size of the intermediate structures allocated by the weak hash table to hold all those weak references (the weak references themselves are not “reachable” by the GC). As the hash table does not shrink automatically when the references in it…

It seems a bit suspicious that the reachable words are exactly the same - as if the strings in the set are not considered reachable because they are behind a weak reference. So maybe the number for the large set is too small and indeed only intermediate data structures are reported. It’s still a bit…

Calling Pool.clear improves the situation but it is not a general solution because it removes all elements. In general you want to adjust to the current size (which in general is not empty) after garbage collection. However, I need to try to insert a few elements again to give the implementation th…

One thing in this code that I see is that there’s no attempt to remove an empty cell itself from the collection. Thus, this code appears to produce empty cells in the end. Do you think there should be a finalizer for each cell that would be run and remove that cell from the collection? The hashes…

This would be a bug in the standard library then: Each value may magically disappear from the set when it is not used by the rest of the program any more

Memory footprint of a weak set

Learning

nojb March 29, 2020, 6:49pm 4

Did you try with Pool.clear ?

Topic		Replies	Views
Weak (object refs/ptrs) in OCaml? Learning	8	723	April 10, 2023
How to measure the memory occupied by a given data structure? Learning gc	9	2594	May 18, 2018
OCaml runtime: hash cons‘ing for strings? Learning	3	866	May 29, 2020
Type for mutable sets Learning	4	804	May 31, 2022
Gc.finalise and let open struct .. end Learning gc	4	603	April 16, 2021

Memory footprint of a weak set

Related topics