[Python-Dev] bdb.py trace C implementation? (original) (raw)

Guido van Rossum guido at python.org
Thu Apr 2 00:48:59 CEST 2009

On Wed, Apr 1, 2009 at 3:25 PM, Benjamin Peterson <benjamin at python.org> wrote:

2009/4/1 David Christian <david.christian at gmail.com>:

Hi all, I've recently written a C version of the trace function used in figleaf (the coverage tool written by Titus).  After a few rewrites to add in caching, etc, it gives users a significant speedup.  One person stated that switching to the C version caused coverage to decrease from a 442% slowdown to only a 56% slowdown.

You can see my C implementation at:  http://github.com/ctb/figleaf/blob/e077155956c288b68704b09889ebcd675ba02240/figleaf/coverage.c (Specific comments about the implementation welcome off-list). I'd like to attempt something similar for bdb.py (only for the trace function).  A naive C trace function which duplicated the current python function should speed up bdb significantly.  I would initially write the smallest part of the C implementation that I could. Basically the tracing function would call back out to python at any point where a line requires action. I'd be willing to maintain the C implementation.  I would be willing to write those tests that are possible as well. Is this something that would be likely to be accepted? Generally debugging doesn't require good performance, so this is definitely low priority. However, if you can contribute it, I don't have a problem with it.

Tracing has other uses besides debugging though. In particular, coverage, which usually wants per-line data. Also, sometimes if you set a breakpoint in a function it turns on tracing for the entire function. This can sometimes be annoyingly slow. So, personally, I am more positive than that, and hope it will make it in.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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