[Python-Dev] RFC: PEP 445: Add new APIs to customize Python memory allocators

[Victor Stinner]

Le jeudi 20 juin 2013, Nick Coghlan a écrit :
>
> > Is PyMemMappingAllocator complete enough for your usage at CCP Games?
>
> Can we go back to calling this the "Arena" allocator? Or at least
> "Mapped"? When I see "Mapping" in the context of Python I think of the
> container API, not a memory allocation API.
>
This function is written to be able to use mmap() and VirtualAlloc(). There
is no Python function to use directly this allocator yet, but I chose
"memory mapping" name because it is very different than the heap and it may
be useful for other functions than pymalloc.

If I change the name, it would be called PyObject_SetArenaAllocator() with
a PyObjectArenaAllocator structure. I'm not sure that PyMemMappingAllocator
API is future-proof, so I'm fine to call it "arena" again.

> > I hope that the PEP 445 is flexible enough to allow you to decide
> > which functions are hooked and replaced, and which functions will be
> > leaved unchanged. That's why I'm not in favor of the "Make
> > PyMem_Malloc() reuse PyMem_RawMalloc() by default" alternative.
>
> It's also why I'm in favour of the "domain" API rather than separate
> functions.
>
> 1. In the initial iteration, just have the three basic domains (raw,
> interpreter, objects). Replacing allocators for third party libraries is
> the responsibility of embedding applications.
>
> 2. In a later iteration, add "PyMem_AddDomain" and "PyMem_GetDomains" APIs
> so that extension modules can register new domains for wrapped libraries.
> Replacing allocators is still the responsibility of embedding applications,
> but there's a consistent API to do it.
>
> (Alternatively, we could do both now)
>
How would you use an allocator of a new domain? PyMemBlockAllocator
structure is not convinient, and if Py_GetAllocator() only once, you may
loose a hook installed later.

Victor
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