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

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Date:	Fri, 17 Jun 2016 17:24:46 +1000
From:	Balbir Singh <bsingharora@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Rik van Riel <riel@...hat.com>,
	Sangwoo Park <sangwoo2.park@....com>
Subject: Re: [PATCH v1 3/3] mm: per-process reclaim



On 14/06/16 01:06, Johannes Weiner wrote:
> 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

Yes, I'd agree. cgroups can group many tasks, but the group size can be
1 as well. Could you try the same test with the recommended approach and
see if it works as desired? 

Balbir Singh