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Date:   Tue, 23 Jun 2020 11:07:21 +0200
From:   Oleksandr Natalenko <oleksandr@redhat.com>
To:     Minchan Kim <minchan@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        linux-mm <linux-mm@kvack.org>, linux-api@vger.kernel.org,
        Suren Baghdasaryan <surenb@google.com>,
        Tim Murray <timmurray@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,
        David Rientjes <rientjes@google.com>,
        Arjun Roy <arjunroy@google.com>
Subject: Re: [PATCH v8 0/4]  introduce memory hinting API for external process
Message-ID: <20200623090721.5owt4cxjji6isqe3@butterfly.localdomain>
References: <20200622192900.22757-1-minchan@kernel.org>
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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/

What "next" tag this (v8) submission is based on please?

> * from v6 - https://lore.kernel.org/linux-api/20200219014433.88424-1-minchan@kernel.org/
>   * fix comments and descriptions - Suren
>   * Add Reviewed-by - Suren
>   * fix build break reported by 0-day
> 
> * from v5 - https://lore.kernel.org/linux-mm/20200214170520.160271-1-minchan@kernel.org/
>   * use null task and requestor's mm for io_madvise - Jann and Jens
>   * use right commit description for moving pidfd_get_pid - Christoph
> 
> * from v4 - https://lore.kernel.org/linux-mm/20200212233946.246210-1-minchan@kernel.org/
>   * pass mm down to functions, not accessing task->mm - Jann
>   * clean up - Alexander
>   * add Reviewed-by - Alexander, SeongJae
>   * patch reordering
> 
> * from v3 - https://lore.kernel.org/linux-mm/20200128001641.5086-1-minchan@kernel.org/
>   * verify task->mm aftere access_mm - Oleg
>   * split some patches for easy review - Alexander
>   * clean up fatal signal checking - Suren
> 
> * from v2 - https://lore.kernel.org/linux-mm/20200116235953.163318-1-minchan@kernel.org/
>   * check signal callee and caller to bail out - Kirill Tkhai
>   * put more clarification for justification of new API
> 
> * from v1 - https://lore.kernel.org/linux-mm/20200110213433.94739-1-minchan@kernel.org/
>   * fix syscall number - SeongJae
>   * use get_pid_task - Kirill Tkhai
>   * extend API to support pid as well as pidfd - Kirill Tkhai
> 
> Minchan Kim (4):
>   mm/madvise: pass task and mm to do_madvise
>   pid: move pidfd_get_pid() to pid.c
>   mm/madvise: introduce process_madvise() syscall: an external memory
>     hinting API
>   mm/madvise: check fatal signal pending of target process
> 
>  arch/alpha/kernel/syscalls/syscall.tbl      |   1 +
>  arch/arm/tools/syscall.tbl                  |   1 +
>  arch/arm64/include/asm/unistd.h             |   2 +-
>  arch/arm64/include/asm/unistd32.h           |   2 +
>  arch/ia64/kernel/syscalls/syscall.tbl       |   1 +
>  arch/m68k/kernel/syscalls/syscall.tbl       |   1 +
>  arch/microblaze/kernel/syscalls/syscall.tbl |   1 +
>  arch/mips/kernel/syscalls/syscall_n32.tbl   |   1 +
>  arch/mips/kernel/syscalls/syscall_n64.tbl   |   1 +
>  arch/mips/kernel/syscalls/syscall_o32.tbl   |   1 +
>  arch/parisc/kernel/syscalls/syscall.tbl     |   1 +
>  arch/powerpc/kernel/syscalls/syscall.tbl    |   1 +
>  arch/s390/kernel/syscalls/syscall.tbl       |   1 +
>  arch/sh/kernel/syscalls/syscall.tbl         |   1 +
>  arch/sparc/kernel/syscalls/syscall.tbl      |   1 +
>  arch/x86/entry/syscalls/syscall_32.tbl      |   1 +
>  arch/x86/entry/syscalls/syscall_64.tbl      |   2 +
>  arch/xtensa/kernel/syscalls/syscall.tbl     |   1 +
>  fs/io_uring.c                               |   2 +-
>  include/linux/compat.h                      |   4 +
>  include/linux/mm.h                          |   3 +-
>  include/linux/pid.h                         |   1 +
>  include/linux/syscalls.h                    |   2 +
>  include/uapi/asm-generic/unistd.h           |   4 +-
>  kernel/exit.c                               |  17 --
>  kernel/pid.c                                |  17 ++
>  kernel/sys_ni.c                             |   2 +
>  mm/madvise.c                                | 190 +++++++++++++++++---
>  28 files changed, 217 insertions(+), 46 deletions(-)
> 
> -- 
> 2.27.0.111.gc72c7da667-goog
> 

-- 
  Best regards,
    Oleksandr Natalenko (post-factum)
    Principal Software Maintenance Engineer