[Python-Dev] CPython optimization: storing reference counters outside of objects (original) (raw)

geremy condra debatem1 at gmail.com
Tue May 24 19:09:07 CEST 2011

On Tue, May 24, 2011 at 8:44 AM, Terry Reedy <tjreedy at udel.edu> wrote:

On 5/24/2011 8:25 AM, Sturla Molden wrote:

Artur Siekielski is not talking about cache locality, but copy-on-write fork on Linux et al.

When reference counts are updated after forking, memory pages marked copy-on-write are copied if they store reference counts. And then he quickly runs out of memory. He wants to put reference counts and PyObjects in different pages, so only the pages with reference counts get copied. I don't think he cares about cache locality at all, but the rest of us do :-) It seems clear that separating reference counts from objects satisfies a specialized need and should be done in a spedial, patched version of CPython rather than the general distribution.

I'm not sure I agree, especially given that the classical answer to GIL woes has been to tell people to fork() themselves. There has to be a lot of code out there that would benefit from this.

Geremy Condra

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