linux-kernel - Re: [PATCH v7 0/7] introduce memory hinting API for external process

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Date:   Mon, 2 Mar 2020 13:16:18 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
        linux-api@...r.kernel.org, oleksandr@...hat.com,
        Suren Baghdasaryan <surenb@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        Daniel Colascione <dancol@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        John Dias <joaodias@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Jann Horn <jannh@...gle.com>,
        alexander.h.duyck@...ux.intel.com, sj38.park@...il.com
Subject: Re: [PATCH v7 0/7] introduce memory hinting API for external
 process

On Mon,  2 Mar 2020 11:36:23 -0800 Minchan Kim <minchan@...nel.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?