Re: [PATCH v6 0/7] introduce memory hinting API for external process

On Wed, Feb 19, 2020 at 12:01 PM Andrew Morton
[off-list ref] wrote:

On Tue, 18 Feb 2020 17:44:26 -0800 Minchan Kim [off-list ref] 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.

This patchset doesn't seem to be getting a lot of interest from other
potential users?  It seems very specialized.  Are there or will there
ever be any users of this apart from one Android daemon?

Don't know if this can be considered another user since it's still in
the Android realm of things.
I'm interested in extending process_madvise() to support MADV_DONTNEED
to expedite memory ripping of a process killed by Android Low Memory
Killer. But for that I need process_madvise() to be accepted first.
IIRC Crome team was interested in these madv hints as well at some point...

Also, it doesn't terribly hard for ActivityManagerService to tell
another process "now run madvise with these arguments".  Please explain
why this is not practical in ActivityManagerService and also within
other potential users of this syscall.