showell <showel...@yahoo.com> added the comment: I am attaching a new patch that does not add a new element to PyListObject, roughly following a technique that Antoine Pitrou suggested on python-dev. When I want to lazily avoid a memmove under the new patch, I set the MSB on allocated and store the original ob_item pointer in the new ob_item[-1].
On the advice of Daniel, I ran the new patch against the Unladen benchmark suite. The results were pretty neutral--never more than a 1% penalty but no significant gains either. I did not expect to see gains, for the obvious reason that I am improving performance on an operation that folks have been encouraged to work around. The new patch continues to do well on microbenchmarks. The new patch fails one test in test_sys related to the 12 byte garbage collection header. The failure is definitely introduced by my patch, but I am not sure what it's doing wrong. All other tests pass. Because the new code piggybacks on top of of allocated instead of creating a new variable in PyListObject, the new code is a bit more complex than the original patch, which is unfortunate. There are probably some opportunities for making the new code simpler. ---------- Added file: http://bugs.python.org/file16033/DIFF_NO_EXTRA_MEM _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue7784> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
