linux-kernel - Re: [PATCH v8 0/4] introduce memory hinting API for external process

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Date:   Mon, 22 Jun 2020 12:36:35 -0700
From:   Minchan Kim <minchan@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>, oleksandr@...hat.com
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        linux-mm <linux-mm@...ck.org>, linux-api@...r.kernel.org,
        oleksandr@...hat.com, Suren Baghdasaryan <surenb@...gle.com>,
        Tim Murray <timmurray@...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,
        David Rientjes <rientjes@...gle.com>,
        Arjun Roy <arjunroy@...gle.com>
Subject: Re: [PATCH v8 0/4]  introduce memory hinting API for external process

On Mon, Jun 22, 2020 at 12:28:56PM -0700, Minchan Kim 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} 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.
> 
> * from v7 -  http://lore.kernel.org/r/20200302193630.68771-1-minchan@kernel.org
>   * dropping pid support from new syscall and fold releated patches into syscall patch
>   * dropping KSM patch by discussion - Oleksandr, I lost the discussion.
>     Please resend the single patch against of the patchset if you resolves the discussion.
>     https://lore.kernel.org/linux-api/20200302193630.68771-8-minchan@kernel.org/

Oleksandr, it seems you discussed something with Vlastimil but couldn't
find conclustion yet and Since Jann put an a new note in the thread,
I detach the patch from this patchset.

Please send the KSM patch based on this patchset if you belive there is
no need to be actionable for comments.