
Armin Rigo <arigo@tunes.org> writes:
Hello Martin,
On Sun, Nov 02, 2003 at 08:05:55PM +0100, Martin v. L?wis wrote:
More than that in the good cases. Something I forgot was that you'd probably have to knock variable length types on the head.
Why?
Assuming "to knock on the head" means "to put an end to":
If you put all objects of the same type into a pool, you really want all objects to have the same side, inside a pool. With that assumption, garbage objects can be reallocated without causing fragmentation. If objects in a pool have different sizes, it is not possible to have an efficient reallocation strategy.
"Not easy" would have been more appropriate. It is still basically what malloc() does.
Well, yeah, but as Tim said pymalloc gets its wins from assuming that each allocation is the same size. You could combine my idea with some other allocation scheme, certainly, but given the relative paucity of variable length types and the reduction in allocator overhead using something like pymalloc gives us, I think it might just be easier to not do them any more. Of course, I don't see myself having any time to play with this idea any time soon, and it's probably not really beefy enough to get a masters thesis from, so maybe we'll never know.
One way would be to use Python's current memory allocator, by adapting it to sort objects into pools not only according to size but also according to type.
That's pretty much what I was suggesting.
What seems to me like a good solution would be to use one relatively large "arena" per type and Python's memory allocator to subdivide each arena. If each arena starts at a pointer address which is properly aligned, then *(p&MASK) gives you the type of any object, and possibly even without much cache-miss overhead because there are not so many arenas in total (probably only 1-2 per type in common cases, and arenas can be large).
Hmm, maybe. I'm not going to make guesses about that one :-) Cheers, mwh -- ... Windows proponents tell you that it will solve things that your Unix system people keep telling you are hard. The Unix people are right: they are hard, and Windows does not solve them, ... -- Tim Bradshaw, comp.lang.lisp