Re: [PATCH v1 3/3] mm: per-process reclaim

[Johannes Weiner]

Hi Minchan,

On Mon, Jun 13, 2016 at 04:50:58PM +0900, Minchan Kim wrote:
> These day, there are many platforms available in the embedded market
> and sometime, they has more hints about workingset than kernel so
> they want to involve memory management more heavily like android's
> lowmemory killer and ashmem or user-daemon with lowmemory notifier.
> 
> This patch adds add new method for userspace to manage memory
> efficiently via knob "/proc/<pid>/reclaim" so platform can reclaim
> any process anytime.

Cgroups are our canonical way to control system resources on a per
process or group-of-processes level. I don't like the idea of adding
ad-hoc interfaces for single-use cases like this.

For this particular case, you can already stick each app into its own
cgroup and use memory.force_empty to target-reclaim them.

Or better yet, set the soft limits / memory.low to guide physical
memory pressure, once it actually occurs, toward the least-important
apps? We usually prefer doing work on-demand rather than proactively.

The one-cgroup-per-app model would give Android much more control and
would also remove a *lot* of overhead during task switches, see this:
https://lkml.org/lkml/2014/12/19/358