On Fri, Jan 20, 2017 at 8:17 PM, Victor Stinner
<victor.stin...@gmail.com> wrote:
> 2017-01-20 11:49 GMT+01:00 INADA Naoki <songofaca...@gmail.com>:
>> Report is here
>> https://gist.github.com/methane/ce723adb9a4d32d32dc7525b738d3c31
>
> Very interesting report, thanks!
>
>> My thoughts are:
>>
>> * Interning (None,) seems worth enough.
>
> I guess that (None,) comes from constants of code objects:
>
>>>> def f(): pass
> ...
>>>> f.__code__.co_consts
> (None,)
>
>
>> * There are many empty dicts. Allocating ma_keys lazily may reduce
>> memory usage.
>
> Would you be able to estimate how many bytes would be saved by this
> change? With the total memory usage to have an idea of the %.
>
Smallest dictkeysobject is 5*8 + 8 + (8 * 3 * 5) = 168 bytes.
1600 empty dicts = 268800 bytes.
Unlike tuples bound to code objects, I don't think this is so important
for cache hit rate. So tuple is more important than dict.
> By the way, it would help if you can add the total memory usage
> computed by tracemalloc (get_traced_memory()[0]) in your report.
>
Oh, nice to know it. I'll use it next time.
> About empty dict, do you expect that they come from shared keys?
> Anyway, if it has a negligible impact on the performance, go for it
> :-)
>
>
>> but other namespaces or annotations, like ('return',) or ('__wrapped__',)
>> are not shared
>
> Maybe we can intern all tuple which only contains one string?
Ah, it's dict's key. I used print(tuple(d.keys())) to count dicts.
>
> Instead of interning, would it be possible to at least merge
> duplicated immutable objects?
>
I meant sharing same object, I didn't meant using dict or adding bit
for interning like
interned strings. So I think we have same idea.
>
>> * Most large strings are docstring. Is it worth enough that option
>> for trim docstrings, without disabling asserts?
>
> Yeah, you are not the first one to propose. The problem is to decide
> how to name the .pyc file.
>
> My PEP 511 proposes to add a new -O command line option and a new
> sys.implementation.optim_tag string to support this feature:
> https://www.python.org/dev/peps/pep-0511/
>
> Since the code transformer part of the PEP seems to be controversal,
> maybe we should extract only these two changes from the PEP and
> implement them? I also want -O noopt :-) (disable the peephole
> optimizer)
>
> Victor
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