[Python-Dev] Proposal to drop f_tstate

[Christian Tismer]

Dear developers,

For years, there has been a f_tstate field in frames.

During my implementation of thread pickling for Stackless,
I investigated how much use is made of this field.
I found out that it is only used in rare cases, only, and can
be most probably replaced by PyThreadState_GET() in the
six or seven cases where it is touched at all.

f_tstate would make sense if PyThreadState_GET() wasn't
such a cheap macro. It also would make sense if it were used
somewhere to assure proper allocation of a frame to its tstate.
But this is nowhere used.
In the case of Stackless, f_tstate turns out to be even a
drawback, since non-recursively called frames can be freely
moved between real threads, and I'm saving updates to f_tstate
already, simply by removing it.

I also didn't find any external module that uses f_tstate.

Therefore, I hereby propose to remove this frame field,
in order to save space.

I also offer to provide the simple patch, right now.

cheers -- chris

-- 
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