[Python-ideas] Save memory when forking with *really* immutable objects
jimjjewett at gmail.com
Wed Mar 14 23:07:14 CET 2012
On Mon, Mar 12, 2012 at 8:10 PM, Larry Hastings <larry at hastings.org> wrote:
> The obvious first step: add a magical reference count number that never
> changes, called Py_REF_ETERNAL.
If you have a magic number, you need to check before doing the update;
at some point in the distant past, that was considered too expensive
because it is done so often.
But once you do pay the cost of a more expensive refcount update, this
isn't the only optimization available. For example, the incref/decref
can be delayed or batched up, which can help with remote objects or
incremental garbage collection. Gating reference acquisition may also
be re-purposed to serve as thread-locking, or to more efficiently
support Software Transactional Memory.
> Martin suggests that this wouldn't help unless we could concentrate the
> Py_REF_ETERNAL objects in their own memory pools in the small block
Right; it makes sense to have the incref/decref function be per-arena,
or at least per page or some such.
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