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Date:   Mon, 2 Mar 2020 13:42:28 -0800
From:   Minchan Kim <minchan@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
        linux-api@vger.kernel.org, oleksandr@redhat.com,
        Suren Baghdasaryan <surenb@google.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>,
        Jann Horn <jannh@google.com>,
        alexander.h.duyck@linux.intel.com, sj38.park@gmail.com
Subject: Re: [PATCH v7 0/7] introduce memory hinting API for external process
Message-ID: <20200302214228.GB71660@google.com>
References: <20200302193630.68771-1-minchan@kernel.org>
 <20200302131618.b0f9f0e76d53a69184321884@linux-foundation.org>
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On Mon, Mar 02, 2020 at 01:16:18PM -0800, Andrew Morton wrote:
> On Mon,  2 Mar 2020 11:36:23 -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.
> > 
> > To solve the concern, this patch introduces new syscall - process_madvise(2).
> > Bascially, it's same with madvise(2) syscall but it has some differences.
> > 
> > 1. It needs pidfd of target process to provide the hint
> > 2. It supports only MADV_{COLD|PAGEOUT|MERGEABLE|UNMEREABLE} at this moment.
> >    Other hints in madvise will be opened when there are explicit requests from
> >    community to prevent unexpected bugs we couldn't support.
> > 3. Only privileged processes can do something for other process's address
> >    space.
> > 
> > For more detail of the new API, please see "mm: introduce external memory hinting API"
> > description in this patchset.
> 
> Thanks, I grabbed these.
> 
> I massaged the patch titles significantly - mainly to alert readers to
> the fact that we're proposing a new syscall.
> 
> Is a manpage for process_madvise(2) being prepared?

I will prepare it, Thanks!