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gh-103200: Fix performance issues with zipimport.invalidate_caches()
#103208
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arhadthedev
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This PR fixes the over-eagerness of the original
zipimport.invalidate_caches()implementation.Currently in
zipimport.invalidate_caches(), the cache of zip files is repopulated at the point of invalidation. This causes cache invalidation to be slow, and violates the semantics of cache invalidation which should simply clear the cache. Cache repopulation should occur on the next access of files.There are three relevant events to consider:
invalidate_caches()is calledEvents (1) and (2) should be fast, while event (3) can be slow since we're repopulating a cache. In the original implementation, (1) and (3) are fast, but (2) is slow.
This PR shifts the cost of reading the directory out of cache invalidation and back to cache access, while avoiding any behaviour change introduced in Python 3.10+ and keeping the common path of reading the cache performant.
Ideally, this fix should be backported to Python 3.10+.
zipimport.invalidate_caches()implementation causes performance regression forimportlib.invalidate_caches()#103200