[Python-Dev] The "lazy strings" patch

Talin talin at acm.org
Mon Oct 23 06:07:42 CEST 2006

Larry Hastings wrote:
> Martin v. Löwis wrote:

> Let's be specific: when there is at least one long-lived small lazy 
> slice of a large string, and the large string itself would otherwise 
> have been dereferenced and freed, and this small slice is never examined 
> by code outside of stringobject.c, this approach means the large string 
> becomes long-lived too and thus Python consumes more memory overall.  In 
> pathological scenarios this memory usage could be characterized as "insane".
> True dat.  Then again, I could suggest some scenarios where this would 
> save memory (multiple long-lived large slices of a large string), and 
> others where memory use would be a wash (long-lived slices containing 
> the all or almost all of a large string, or any scenario where slices 
> are short-lived).  While I think it's clear lazy slices are *faster* on 
> average, its overall effect on memory use in real-world Python is not 
> yet known.  Read on.

I wonder - how expensive would it be for the string slice to have a weak 
reference, and 'normalize' the slice when the big string is collected? 
Would the overhead of the weak reference swamp the savings?

-- Talin

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