[Python-Dev] Design Philosophy: Performance vs Robustness/Maintainability (original) (raw)

Ethan Furman ethan at stoneleaf.us
Tue Jul 18 12:27:13 EDT 2017

On 07/18/2017 09:16 AM, Antoine Pitrou wrote:

On Tue, 18 Jul 2017 09:08:08 -0700 Ethan Furman <ethan at stoneleaf.us> wrote:

Nick Coughlan: ------------- It is "Nick Coghlan" not "Coughlan".

Argh. Sorry, Nick, and thank you, Antoine!

As another example of this: while trading the global import lock for per-module locks eliminated most of the old import deadlocks, it turns out that it also left us with some fairly messy race conditions and more fragile code (I still count that particular case as a win overall, but it definitely raises the barrier to entry for maintaining that code).

Unfortunately, these are frequently cases where the benefits are immediately visible (e.g. faster benchmark results, removing longstanding limitations on user code), but the downsides can literally take years to make themselves felt (e.g. higher defect rates in the interpreter, subtle bugs in previously correct user code that are eventually traced back to interpreter changes). I'll reply here again: the original motivation for the per-module import lock was not performance but correctness.

I meant that as an example of the dangers of increased code complexity.

-- Ethan

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