[Python-Dev] Have a big machine and spare time? Here's a possible Python bug. (original) (raw)

Larry Hastings larry at hastings.org
Sun May 26 05:29:14 EDT 2019

On 5/22/19 12:15 PM, Tim Peters wrote:

There's a Stackoverflow report[1] I suspect is worth looking into, but it requires far more RAM (over 80GB) than I have). [...] But, for a start, it would be good to know if anyone else can actually reproduce the problem.

[1] https://stackoverflow.com/questions/56228799/python-hangs-indefinitely-trying-to-delete-deeply-recursive-object

I have a computer with two Xeon CPUs and 256GB of RAM.  So, even though it's NUMA, I still have 128GB of memory per CPU.  It's running a "spin" of Ubuntu 18.10.

I compiled a fresh Python 3.7.3 --with-optimizations.  I copied the sample program straight off the StackOverflow page.  The program ran for about five and a half hours then exited normally.

During the run it printed:

This gets printed!
This doesn't get printed

Statistics reported by "time":

19811.05s user 123.56s system 99% cpu 5:32:15.04 total

Checking in on it now and then, peak observed memory usage (as reported by "top") was just under 80GB.

I take it that the interesting part was confirming that "This doesn't get printed" gets printed when you have enough RAM for the program to run to completion.  So I guess there's no bug here? Just an observation about CPython's garbage collector being kinda slow?  Or maybe CPython gc

//arry/

-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20190526/f2d10ec9/attachment.html>

More information about the Python-Dev mailing list