[Python-Dev] requirements for moving import over to importlib? (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Tue Feb 7 21:49:48 CET 2012

On Tue, 7 Feb 2012 15:07:24 -0500 Brett Cannon <brett at python.org> wrote:

Now I'm going to be upfront and say I really did not want to have this performance conversation now as I have done NO profiling or analysis of the algorithms used in importlib in order to tune performance (e.g. the function that handles case-sensitivity, which is on the critical path for importing source code, has a platform check which could go away if I instead had platform-specific versions of the function that were assigned to a global variable at startup).

From a cursory look, I think you're gonna have to break (special-case) some abstractions and have some inner loop coded in C for the common cases.

That said, I think profiling and solving performance issues is critical before integrating this work. It doesn't need to be done by you, but the python-dev community shouldn't feel strong-armed to solve the issue.

IOW I really do not look forward to someone saying "importlib is so much slower at importing a module containing pass" when (a) that never happens, and (b) most programs do not spend their time importing but instead doing interesting work.

Well, import time is so important that the Mercurial developers have written an on-demand import mechanism, to reduce the latency of command-line operations.

But it's not only important for Mercurial and the like. Even if you're developing a Web app, making imports slower will make restarts slower, and development more tedious in the first place.

So, if there is going to be some baseline performance target I need to hit to make people happy I would prefer to know what that (real-world) benchmark is and what the performance target is going to be on a non-debug build.

Regards

Antoine.

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