#12313: Fix yet another memory leak caused by caching of coercion data
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Reporter: SimonKing | Owner:
Type: defect | Status:
needs_review
Priority: major | Milestone: sage-5.3
Component: memleak | Resolution:
Keywords: coercion weak dictionary | Work issues:
Report Upstream: N/A | Reviewers: Simon King,
Jean-Pierre Flori, John Perry
Authors: Simon King, Jean-Pierre Flori | Merged in:
Dependencies: #11521, #11599, #12969, #12215 | Stopgaps:
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Comment (by nbruin):
Too bad ... We never did positively confirm that the problem here was some
method on a key getting '''called'''. The patch doesn't help for the
polybori problem. I suspect it really is a double memory release somewhere
that simply didn't ever occur before because the memory didn't get
released in the first place? (perhaps python doesn't deallocate all memory
upon exit? why would they?
I don't think a more fancy implementation of a safeweakvaluedict would
work either. By keeping references to all keys while *clearing* the
dictionary (that's just the clear that's inherited on dict), I think we
are avoiding all calls to keys. Purging a dict doesn't involve key lookups
and deleting the keys afterwards is just that. That should be possible. By
then we're not holding weakrefs on them anymore, so no callbacks.
So, while I still think the current `WeakValueDict` design has a silly
callback, the only problem with it that we have actually observed can be
solved with a well-timed `gc.collect()`.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12313#comment:220>
Sage <http://www.sagemath.org>
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