linux-kernel - Re: [PATCH v2 1/1] mm/madvise: add MADV_F_COLLAPSE_LIGHT to process

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Date: Mon, 22 Jan 2024 22:14:11 +0800
From: Lance Yang <ioworker0@...il.com>
To: Michal Hocko <mhocko@...e.com>
Cc: akpm@...ux-foundation.org, zokeefe@...gle.com, david@...hat.com, 
	songmuchun@...edance.com, shy828301@...il.com, peterx@...hat.com, 
	mknyszek@...gle.com, minchan@...nel.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] mm/madvise: add MADV_F_COLLAPSE_LIGHT to process_madvise()

On Mon, Jan 22, 2024 at 9:50 PM Michal Hocko <mhocko@...e.com> 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