Re: [PATCH v2 1/1] mm/madvise: add MADV_F_COLLAPSE_LIGHT to process_madvise()

[Lance Yang]

On Mon, Jan 22, 2024 at 9:50 PM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Sat 20-01-24 10:09:32, Lance Yang wrote:
> [...]
> > Hey Michal,
> >
> > Thanks for your suggestion!
> >
> > It seems that the implementation should try but not too hard aligns well
> > with my desired behavior.
>
> The problem I have with this semantic is that it is really hard to
> define and then stick with. Our implementation might change over time
> and what somebody considers good ATM might turn int "trying harder than
> I wanted" later on.
>
> > Non-blocking in general is also a great idea.
> > Perhaps in the future, we can add a MADV_F_COLLAPSE_NOBLOCK
> > flag for scenarios where latency is extremely critical.
>
> Non blocking semantic is much easier to define and maintain. The actual
> allocation/compaction implementation might change as well over time but
> the userspace at least knows that the request will not block waiting for
> any required resources.

I appreciate your insights!

It makes sense that a non-blocking semantic is easier to define and maintain,
providing userspace with the certainty that requests won’t be blocked.

Thanks,
Lance

>
> --
> Michal Hocko
> SUSE Labs