[pypy-issue] [issue927] Task takes more time on nightly than CPython 2.7

[Justin Peel]

Justin Peel <peelpy at gmail.com> added the comment:

This looks like the same gc performance problem that we have with making large 
dicts. Minimark uses card refs at the front of arrays to determine if objects 
need to be examined and possibly moved out of the nursery. Each bit represents 
whether anything was changed in a range of objects in the array behind the 
structure. I believe the size is a little over a hundred. Anyway, it works well 
for appending objects to lists, but when adding items to dicts and sets, objects 
are added in pseudo-randomly. When creating huge dicts/sets, basically the whole 
low level array behind the dict/set is checked for every minor collection.

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nosy: +justinpeel

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