Re: [PATCH 1/4] mm: Trial do_wp_page() simplification

Peter Xu
2020-09-21T16:31:23Z

On Mon, Sep 21, 2020 at 04:57:38PM +0200, Michal Hocko wrote:
> Switching the order wouldn't make much of a difference right. At least
> not for memcg where all the accounted allocations will still go to
> current's memcg.

I think I'll make it simple to charge the parent directly just like what we do
right now. I do expect that the charged amount could be quite some when
there're a lot pinned pages on the parent process, however hopefully it's
acceptable as it's still a very rare case, and proper MADV_DONTFORK upon pinned
pages on the parent process will eliminate all these charges too.

I actually already prepared some patches. It's definitely bigger than expected
due to the complexity that we held page table locks in copy_one_pte() when
trying to break the cow pages. I don't know whether it would be proper any
more for rc, especially the ending of rcs. Anyway I'll post them out soon
after I did some basic tests, because I think that's something right to do
irrelevant to when it will be merged.

Thanks,

--
Peter Xu