Move stackref buffer to per-eval loop to reduce interp stack usage

Feature or enhancement

Proposal:

The interpreter main loop's stack usage is huge. We should try to reduce it a little. Currently, the stackref buffer takes up 10 words on 64-bit machines. We could lessen that by moving it to the heap (thread state).

This might mean slightly less perf due to worse locality and one memory indirection. So let's benchmark this to be sure.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-138116

从解释器主循环开始，找到提案中提到的 stackref 缓冲区和线程状态。对当前布局和提议的布局进行基准测试，包括栈使用量、局部性或间接访问成本以及性能。只有当测量结果支持这一更改时，才按提议移动 stackref 缓冲区；完成意味着这一点；gh-138116 表明相关工作已经在进行中。