Re: [PATCH] mm/ksm: introduce ksm_enabled for each processg

[CGEL <cgel.zte@gmail.com>]

On Wed, May 18, 2022 at 02:14:28PM +0200, Michal Hocko wrote:
> On Wed 18-05-22 07:40:30, CGEL wrote:
> [...]
> > 2. process_madvise is still a kind of madvise. processs_madvise from
> > another process overrides the intention of origin app code ifself that
> > also calls madvise, which is unrecoverable. For example, if a process "A"
> > which madvises just one part of VMAs (not all) as MERGEABLE run on the OS
> > already, meanwhile, if another process which doesn't know the information
> > of "A" 's MERGEABLE areas, then call process_madvise to advise all VMAs of
> > "A" as MERGEABLE, the original MERGEABLE information of "A" calling madivse
> > is erasured permanently.
> 
> I do not really follow. How is this any different from an external
> process modifying the process wide policy via the proc or any other
> interface?

In this patch, you can see that we didn't modify the flag of any VMA of
the target process, which is different from process_madvise. So it is
easy to keep the original MERGEABLE information of the target process
when we turn back to the default state from the state "always".

> -- 
> Michal Hocko
> SUSE Labs