[Python-Dev] C API for gc.enable() and gc.disable()

[Nick Coghlan]

Martin v. Löwis wrote:
> Antoine Pitrou wrote:
>> Le samedi 21 juin 2008 à 17:49 +0200, "Martin v. Löwis" a écrit : 
>>> I don't think any strategies based on timing will be successful.
>>> Instead, one should count and analyze objects (although I'm unsure
>>> how exactly that could work).
>> Would it be helpful if the GC was informed of memory growth by the
>> Python memory allocator (that is, each time it either asks or gives back
>> a block of memory to the system allocator) ?
> 
> I don't see how. The garbage collector is already informed about memory
> growth; it learns exactly when a container object is allocated or
> deallocated. That the allocator then requests memory from the system
> only confirms what the garbage collector already knew: that there are
> lots of allocated objects. From that, one could infer that it might
> be time to perform garbage collection - or one could infer that all
> the objects are really useful, and no garbage can be collected.

I was wondering whether it might be useful to detect the end of an 
allocation spike: if PyMalloc incremented an internal counter each time 
it requested more memory from the system, then the GC could check 
whether that number had changed on each collection cycle. If the GC goes 
a certain number of collection cycles without more memory being 
requested from the system, then it can assume the allocation spike is 
over and tighten up the default tuning again.

Such a pymalloc counter would provide a slightly more holistic view of 
overall memory usage changes than the container-focused view of the 
cyclic GC.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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