[Python-Dev] Have a big machine and spare time? Here's a possible Python bug.
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 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.
>  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
+ swap = super bombad slow?
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