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References: <20200219014433.88424-1-minchan@kernel.org> <20200219120123.07dda51c29006a892059ccde@linux-foundation.org>
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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Wed, 19 Feb 2020 13:05:27 -0800
Message-ID: <CAJuCfpEAk+kD=Wxn3t9VKZxr5CovvdExL47qkEosyEAMEQ6t+Q@mail.gmail.com>
Subject: Re: [PATCH v6 0/7] introduce memory hinting API for external process
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Minchan Kim <minchan@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, linux-api@vger.kernel.org,
        oleksandr@redhat.com, Tim Murray <timmurray@google.com>,
        Daniel Colascione <dancol@google.com>,
        Sandeep Patil <sspatil@google.com>,
        Sonny Rao <sonnyrao@google.com>,
        Brian Geffon <bgeffon@google.com>,
        Michal Hocko <mhocko@suse.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        John Dias <joaodias@google.com>,
        Joel Fernandes <joel@joelfernandes.org>, sj38.park@gmail.com,
        alexander.h.duyck@linux.intel.com, Jann Horn <jannh@google.com>
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On Wed, Feb 19, 2020 at 12:01 PM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> On Tue, 18 Feb 2020 17:44:26 -0800 Minchan Kim <minchan@kernel.org> wrote:
>
> > Now, we have MADV_PAGEOUT and MADV_COLD as madvise hinting API. With that,
> > application could give hints to kernel what memory range are preferred to be
> > reclaimed. However, in some platform(e.g., Android), the information
> > required to make the hinting decision is not known to the app.
> > Instead, it is known to a centralized userspace daemon(e.g., ActivityManagerService),
> > and that daemon must be able to initiate reclaim on its own without any app
> > involvement.
> >
>
> This patchset doesn't seem to be getting a lot of interest from other
> potential users?  It seems very specialized.  Are there or will there
> ever be any users of this apart from one Android daemon?

Don't know if this can be considered another user since it's still in
the Android realm of things.
I'm interested in extending process_madvise() to support MADV_DONTNEED
to expedite memory ripping of a process killed by Android Low Memory
Killer. But for that I need process_madvise() to be accepted first.
IIRC Crome team was interested in these madv hints as well at some point...

>
> Also, it doesn't terribly hard for ActivityManagerService to tell
> another process "now run madvise with these arguments".  Please explain
> why this is not practical in ActivityManagerService and also within
> other potential users of this syscall.
>
>