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 22:34:51 +0800
From: Lance Yang <ioworker0@...il.com>
To: Michal Hocko <mhocko@...e.com>, "Zach O'Keefe" <zokeefe@...gle.com>
Cc: akpm@...ux-foundation.org, 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, 
	linux-api@...r.kernel.org
Subject: Re: [PATCH v2 1/1] mm/madvise: add MADV_F_COLLAPSE_LIGHT to process_madvise()

Hey Zach,

What do you think about the semantic?

Thanks,
Lance

On Mon, Jan 22, 2024 at 10:14 PM Lance Yang <ioworker0@...il.com> wrote:
>
> 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