Python memory handling

[Chris Mellon]

On 5/31/07, Thorsten Kampe <thorsten at thorstenkampe.de> wrote:
> * Chris Mellon (Thu, 31 May 2007 12:10:07 -0500)
> > > Like:
> > > import pool
> > > pool.free()
> > > pool.limit(size in megabytes)
> > >
> > > Why not letting the user choosing that, why not giving the user more
> > > flexibility ?
> > > I will try later under linux with the latest stable python
> > >
> > > Regards,
> > > FP
> > >
> >
> > The idea that memory allocated to a process but not being used is a
> > "cost" is really a fallacy, at least on modern virtual memory sytems.
> > It matters more for fully GCed languages, where the entire working set
> > needs to be scanned, but the Python GC is only for breaking refcounts
> > and doesn't need to scan the entire memory space.
> >
> > There are some corner cases where it matters, and thats why it was
> > addressed for 2.5, but in general it's not something that you need to
> > worry about.
>
> If it's swapped to disk than this is a big concern. If your Python app
> allocates 600 MB of RAM and does not use 550 MB after one minute and
> this unused memory gets into the page file then the Operating System
> has to allocate and write 550 MB onto your hard disk. Big deal.
>

It happens once, and only in page-sized increments. You'd have to have
unusual circumstances to even notice this "big deal", totally aside
from the unusual and rare conditions that would trigger it.