Ruby <2.7now uses WeakMap too, which prevents memory leaks. #8341
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Ruby <2.7 does not allow non-finalizable objects to be WeakMap keys: https://bugs.ruby-lang.org/issues/16035 We work around this by using a secondary map for Ruby <2.7 which maps the non-finalizable integer to a distinct object. For now we accept that the entries in the secondary map wil never be collected. If this becomes a problem we can perform a GC pass every so often that looks at the contents of the object cache to decide what can be deleted from the secondary map.
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Besides not leaking memory any more, this PR also runs the unit tests faster for Ruby 2.5. So I expect improved performance for Rubies prior to 2.7. |
gerben-s
approved these changes
Feb 25, 2021
This was referenced Mar 7, 2021
This was referenced Mar 12, 2021
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Ruby <2.7 does not allow non-finalizable objects to be WeakMap
keys: https://bugs.ruby-lang.org/issues/16035
We work around this by using a secondary map for Ruby <2.7 which
maps the non-finalizable integer to a distinct object.
For now we accept that the entries in the secondary map wil never
be collected. If this becomes a problem we can perform a GC pass
every so often that looks at the contents of the object cache to
decide what can be deleted from the secondary map.
This also changes the way that object pinning works. We pin objects
when they are frozen so they do not forget their frozen state.
Now we implement this with a simple array in Arena, instead of
making it part of the object cache.
Fixes: #8337