[Python-Dev] Object free lists
tim.one at comcast.net
Tue Jun 15 23:30:57 EDT 2004
> Unfortunately the limit code would be much more complex than in
> frameobject because frameobject does not allocate in blocks.
Ugh -- yup.
> So, we would have to somehow determine if an int block is completely free
> before freeing it. Some different methods:
> 1) Scan each block and count the number of free integers. If the block
> contains only free integers, then free it. This would essentially be the
> code in PyInt_Fini().
> We actually have code that calls PyInt_Fini when we are doing leak
> 2) Alternate to #1, it could avoid scanning entire blocks if it detected
> a used int, and instead manually dissect the free_list iff the entire
> block is free instead of rebuilding free_list from scratch like
> PyInt_Fini() does.
> 3) Add a counter of the number of free ints in PyIntBlock. Free the
> block with this number equals the maximum number of ints in a block.
> The problem with #1 is that it is slow, and one would need to determine
> how often to call it. #2 has the same problem.
> #3 is a little nicer, at the cost of maintaining the counter (which
> should be negligible).
At which point we're getting close to reinventing pymalloc, except not
enough so: since the list of int blocks is singly-linked, it's not
efficient to remove an arbitrary one.
I can't make more time tonight, so I look forward to reading the solution in
the morning <wink>.
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