> So i finally did some tests using Nadeem's code snippet
> from msg133677.  The largest top(1) i ever got was
>    30477  python3      2.7       00:09.77 1    0    18    77    912M+  240K
> but the system is unusable then.

The code I posted was only intended to run on machines with at least
4GB of free memory. The precisionbigmemtest decorator should cause it to
be skipped on machines with less RAM.

> Except for all this i don't understand this thread.
> Isn't that bot the one for which haypo has noticed those
> random failures???

The current status of this issue (as I understand it) is:
* test_zlib's test_big_buffer() is failing sporadically on the AMD64
   Snow Leopard buildbot (http://www.python.org/dev/buildbot/all/builders/AMD64%20Snow%20Leopard%203.x/)
* The cause seems to be a bug in OS X's handling of mmap()'d files, not a
   problem with the Python code.
* Antoine has proposed skipping this test on OS X as a workaround, and
   no-one has objected to this.

I don't think it is necessary to further investigate the behaviour of
Snow Leopard's mmap() - we know that it's broken, and we have a fix.

At the moment, we need someone to actually write and commit the fix.
I would do it myself, but I'm hesitant to commit code without testing it,
and don't have access to a Mac system.