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

Hi Oleksandr,

On Tue, Jun 23, 2020 at 11:07:21AM +0200, Oleksandr Natalenko wrote:

On Mon, Jun 22, 2020 at 12:28:56PM -0700, Minchan Kim wrote:

quoted

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 (local)
  * 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/ (local)

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

It's against on v5.8-rc1-mmots-2020-06-20-21-44 from mmotm - https://github.com/hnaz/linux-mm.git