Hi Stefan, On Sun, Feb 26, 2012 at 09:50, Stefan Behnel <stefan_ml@behnel.de> wrote:
Looking at Py_DecRef(), however, left me somewhat baffled. I would have expected this to be the most intensively tuned function in all of cpyext, but it even started with this comment: (...)
Indeed, it's an obvious starting place if we want to optimize cpyext (which did not occur at all so far). You are welcome to try. Note that the JIT has nothing to do here: we cannot JIT any code written in C, and it makes no sense to apply the JIT on a short RPython callback alone. But because most of the code in module/cpyext/ is RPython code, it means it gets turned into equivalent C code statically, with (as you noticed) the debugging checks constant-folded away. The first thing to try would be to rethink how the PyPy object and the PyObject are linked together. Right now it's done with two (possibly weak) dictionaries, one for each direction. We can at least improve the situation by having a normal field in the PyObject pointing back to the PyPy object. This needs to be done carefully but can be done. The issue is that the GC needs to know about this field. It would probably require something like: allocate some GcArrays of PyObject structures (not pointers, directly PyObjects --- which have all the same size here, so it works). Use something like 100 PyObject structures per GcArray, and collect all the GcArrays in a global list. Use a freelist for dead entries. If you allocate each GcArray as "non-movable", then you can take pointers to the PyObjects and pass them to C code. As they are inside the regular GcArrays, they are GC-tracked and can contain a field that points back to the PyPy object. A bientôt, Armin.