First of all, this is just deprecating direct access of `ob_shash`. This makes users need to use `PyObject_Hash()`.
We don't make the final decision about removing it. We just make we can remove it in Python 3.13.

RAM and CACHE efficiency is not the only motivation for this.
There is a discussion about (1) increasing CoW efficiency, and (2) sharing data between subinterpreters after per-interpreter GIL.
Removing ob_shash will help them, especially about the (2).

But if we stop using bytes objects in code objects by Python 3.13, there is no need to remove ob_shash.


> If put a bytes object into multiple dicts/sets, the hash need to be computed multiple times. This seems a common usage.

Doesn't it lose only some milliseconds?
I posted remove-bytes-hash.patch in this issue. Would you measure how this affects whole application performance rather than micro benchmarks?