Hello.

On Mon, Jun 22, 2020 at 12:36:35PM -0700, Minchan Kim 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)

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.

I don't think we came to some definite conclusion, but I'll try to implement
Vlastimil's suggestion and then send it separately for evaluation.

Lets keep KSM bit out of your submission so I won't slow it down.

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