Hello folks,
this is something I came across earlier this week, but I only found
time today to analyze and write down my understanding. I hope that
Robert Bradshaw has some time to look into this. It is not critical
because the amount of memory not deallocated is a) constant and b)
compared to the other 16 issues I am tracking nor very large.
I opened ticket #557 for this. Here is a copy of the report:
Okay, the problem I found is deep in Cython generated code and
maybe not the fault of Cython, but might be an underlying issue
in Python. For each of the 244 pyx files we have in the tree
we do not deallocate a dictionary. While this isn't a defect
per se it makes the valgrind output more noise and therefor
more difficult to parse.
The example output below is from rational.pyx. The function
initrational
is created via Cython (there is no init-method, but that comes out of
the creation of the class as far as I can tell):
==25825== 3,072 bytes in 1 blocks are still reachable in loss record
2,268 of 2,539
==25825== at 0x4A05809: malloc (vg_replace_malloc.c:149)
==25825== by 0x43F179: dictresize (dictobject.c:513)
==25825== by 0x45B00C: PyType_Ready (typeobject.c:5575)
==25825== by 0x169D79A0: initrational (rational.c:10789)
==25825== by 0x49F762: _PyImport_LoadDynamicModule (importdl.c:53)
==25825== by 0x49D63E: import_submodule (import.c:2394)
==25825== by 0x49DB11: load_next (import.c:2214)
==25825== by 0x49DD6E: import_module_level (import.c:2002)
==25825== by 0x49E1A4: PyImport_ImportModuleLevel (import.c:2066)
==25825== by 0x47D5D8: builtin___import__ (bltinmodule.c:47)
==25825== by 0x4156A2: PyObject_Call (abstract.c:1860)
==25825== by 0x47DB71: PyEval_CallObjectWithKeywords (ceval.c:3433)
The exact line from rational.c:10789 is:
if (PyType_Ready(&__pyx_type_8rational_Rational) < 0) {__pyx_filename
= __pyx_f[1]; __pyx_lineno = 126; goto __pyx_L1;}
It mentions line 126 which in rational.pyx is:
cdef class Rational(sage.structure.element.FieldElement):
So can be dereference the class somehow upon exit? Looking
at valgrind-sessions from python it appears that this is
possible because otherwise there would be a large number of
leak dictionaries from the buildin c-libraries.
Cheers,
Michael
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