Cache a bounded number of recently-created parents.

[robertwb]

Cache a bounded number of recently-created parents to avoid repeated re-creation when strong references are not kept.

Related: #715, #14072, #14058.

CC: @nbruin @simon-king-jena @jpflori

Component: memleak

Author: Robert Bradshaw

Issue created by migration from https://trac.sagemath.org/ticket/14073

[simon-king-jena]

comment:1

Attachment: 14073-recently-created.patch.gz

Yep, that's about what I thought would work.

[nbruin]

comment:2

Apart from fixing len(recently_created) at compile-time this may well be a good idea. Main objections:

• It will make debugging that much harder. Given that doctests are small, the parent deletion code will hardly be exercised.
• Do we have good use-cases that show clear benefit from this approach? Given that the frequency of garbage collection in python is rather low, I'd expect that parents will relatively often still be around if they are required soon after deletion.

[robertwb]

comment:3

Replying to @nbruin:

Apart from fixing len(recently_created) at compile-time this may well be a good idea.

len(list) is really fast, much faster than creating a parent, and allows our list to possibly grow or shrink in the future.

Main objections:

• It will make debugging that much harder. Given that doctests are small, the parent deletion code will hardly be exercised.
• Do we have good use-cases that show clear benefit from this approach? Given that the frequency of garbage collection in python is rather low, I'd expect that parents will relatively often still be around if they are required soon after deletion.

I actually agree with both of these objections; I don't think this code should go in unless it's clearly shown to be a problem.