Brett,
On 2016-01-20 1:22 PM, Brett Cannon wrote:
On Wed, 20 Jan 2016 at 10:11 Yury Selivanov <yselivanov...@gmail.com
<mailto:yselivanov...@gmail.com>> wrote:
On 2016-01-18 5:43 PM, Victor Stinner wrote:
> Is someone opposed to this PEP 509?
>
> The main complain was the change on the public Python API, but
the PEP
> doesn't change the Python API anymore.
>
> I'm not aware of any remaining issue on this PEP.
Victor,
I've been experimenting with the PEP to implement a per-opcode
cache in ceval loop (I'll share my progress on that in a few
days). This allows to significantly speedup LOAD_GLOBAL and
LOAD_METHOD opcodes, to the point, where they don't require
any dict lookups at all. Some macro-benchmarks (such as
chameleon_v2) demonstrate impressive ~10% performance boost.
Ooh, now my brain is trying to figure out the design of the cache. :)
Yeah, it's tricky. I'll need some time to draft a comprehensible
overview. And I want to implement a couple more optimizations and
benchmark it better.
BTW, I've some updates (html5lib benchmark for py3, new benchmarks
for calling C methods, and I want to port some PyPy benchmakrs)
to the benchmarks suite. Should I just commit them, or should I
use bugs.python.org?
I rely on your dict->ma_version to implement cache invalidation.
However, besides guarding against version change, I also want
to guard against the dict being swapped for another dict, to
avoid situations like this:
def foo():
print(bar)
exec(foo.__code__, {'bar': 1}, {})
exec(foo.__code__, {'bar': 2}, {})
What I propose is to add a pointer "ma_extra" (same 64bits),
which will be set to NULL for most dict instances (instead of
ma_version). "ma_extra" can then point to a struct that has a
globally unique dict ID (uint64), and a version tag (unit64).
A macro like PyDict_GET_ID and PyDict_GET_VERSION could then
efficiently fetch the version/unique ID of the dict for guards.
"ma_extra" would also make it easier for us to extend dicts
in the future.
Why can't you simply use the id of the dict object as the globally
unique dict ID? It's already globally unique amongst all Python
objects which makes it inherently unique amongst dicts.
We have a freelist for dicts -- so if the dict dies, there
could be a new dict in its place, with the same ma_version.
While the probability of such hiccups is low, we still have
to account for it.
Yury
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
