Mark Shannon <[email protected]> added the comment:
A big -1 to this.
You are asking the whole world to take a hit on both performance and memory
use, in order to save Instagram memory.
The PR uses the term "immortal" everywhere. There is only one reference to
copy-on-write in a comment. Yet this issue about making object headers
immutable.
Immortality and object header immutability are not the same.
If object header immutability is to be a requirement, that needs a PEP.
If it is not requirement, but immortality is, then make the obvious improvement
of changing the branchy code
if (!(obj->refcnt & IMMORTAL_BIT)) {
obj->refcnt++;
}
to the branchless
obj->refcnt += ((obj->refcnt &IMMORTAL_BIT) != 0)
Immortality has advantages because it allows saturating reference counting and
thus smaller object headers, but it is not the same as making the object header
immutable.
----------
nosy: +Mark.Shannon
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Python tracker <[email protected]>
<https://bugs.python.org/issue40255>
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