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From: Lance Yang <ioworker0@gmail.com>
Date: Mon, 22 Jan 2024 22:34:51 +0800
Message-ID: <CAK1f24=7fKU-+xRSOhrJrZ56=YoVfnkONZwNOJRS4yY4SzhANA@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] mm/madvise: add MADV_F_COLLAPSE_LIGHT to process_madvise()
To: Michal Hocko <mhocko@suse.com>, "Zach O'Keefe" <zokeefe@google.com>
Cc: akpm@linux-foundation.org, david@redhat.com, songmuchun@bytedance.com, 
	shy828301@gmail.com, peterx@redhat.com, mknyszek@google.com, 
	minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 
	linux-api@vger.kernel.org
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Hey Zach,

What do you think about the semantic?

Thanks,
Lance

On Mon, Jan 22, 2024 at 10:14=E2=80=AFPM Lance Yang <ioworker0@gmail.com> w=
rote:
>
> On Mon, Jan 22, 2024 at 9:50=E2=80=AFPM Michal Hocko <mhocko@suse.com> wr=
ote:
> >
> > 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 w=
ell
> > > 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 fo=
r
> > any required resources.
>
> I appreciate your insights!
>
> It makes sense that a non-blocking semantic is easier to define and maint=
ain,
> providing userspace with the certainty that requests won=E2=80=99t be blo=
cked.
>
> Thanks,
> Lance
>
> >
> > --
> > Michal Hocko
> > SUSE Labs