linux-kernel - Re: [PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink

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Date:	Tue, 7 Jul 2015 09:38:17 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	PINTU KUMAR <pintu.k@...sung.com>
CC:	<corbet@....net>, <akpm@...ux-foundation.org>, <vbabka@...e.cz>,
	<gorcunov@...nvz.org>, <mhocko@...e.cz>, <emunson@...mai.com>,
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Subject: Re: [PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory feature

On 2015/7/6 22:03, PINTU KUMAR wrote:

> Hi,
> 
>> -----Original Message-----
>> From: Xishi Qiu [mailto:qiuxishi@...wei.com]
>> Sent: Monday, July 06, 2015 3:53 PM
>> To: Pintu Kumar
>> Cc: corbet@....net; akpm@...ux-foundation.org; vbabka@...e.cz;
>> gorcunov@...nvz.org; mhocko@...e.cz; emunson@...mai.com;
>> kirill.shutemov@...ux.intel.com; standby24x7@...il.com;
>> hannes@...xchg.org; vdavydov@...allels.com; hughd@...gle.com;
>> minchan@...nel.org; tj@...nel.org; rientjes@...gle.com;
>> xypron.glpk@....de; dzickus@...hat.com; prarit@...hat.com;
>> ebiederm@...ssion.com; rostedt@...dmis.org; uobergfe@...hat.com;
>> paulmck@...ux.vnet.ibm.com; iamjoonsoo.kim@....com; ddstreet@...e.org;
>> sasha.levin@...cle.com; koct9i@...il.com; mgorman@...e.de; cj@...ux.com;
>> opensource.ganesh@...il.com; vinmenon@...eaurora.org; linux-
>> doc@...r.kernel.org; linux-kernel@...r.kernel.org; linux-mm@...ck.org; linux-
>> pm@...r.kernel.org; cpgs@...sung.com; pintu_agarwal@...oo.com;
>> vishnu.ps@...sung.com; rohit.kr@...sung.com; iqbal.ams@...sung.com
>> Subject: Re: [PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory
>> feature
>>
>> On 2015/7/3 21:20, Pintu Kumar wrote:
>>
>>> This patch provides 2 things:
>>> 1. Add new control called shrink_memory in /proc/sys/vm/.
>>> This control can be used to aggressively reclaim memory system-wide in
>>> one shot from the user space. A value of 1 will instruct the kernel to
>>> reclaim as much as totalram_pages in the system.
>>> Example: echo 1 > /proc/sys/vm/shrink_memory
>>>
>>> 2. Enable shrink_all_memory API in kernel with new
>> CONFIG_SHRINK_MEMORY.
>>> Currently, shrink_all_memory function is used only during hibernation.
>>> With the new config we can make use of this API for non-hibernation
>>> case also without disturbing the hibernation case.
>>>
>>> The detailed paper was presented in Embedded Linux Conference,
>>> Mar-2015 http://events.linuxfoundation.org/sites/events/files/slides/
>>> %5BELC-2015%5D-System-wide-Memory-Defragmenter.pdf
>>>
>>> Scenarios were this can be used and helpful are:
>>> 1) Can be invoked just after system boot-up is finished.
>>> 2) Can be invoked just before entering entire system suspend.
>>> 3) Can be invoked from kernel when order-4 pages starts failing.
>>> 4) Can be helpful to completely avoid or delay the kerenl OOM condition.
>>> 5) Can be developed as a system-tool to quickly defragment entire system
>>>    from user space, without the need to kill any application.
>>>
>>
>> Hi Pintu,
>>
>> How about increase min_free_kbytes and Android lowmemorykiller's level?
>>
> Thanks for the review.
> Actually in Tizen, we don't use Android LMK and we wanted to delay the LMK with
> aggressive direct_reclaim offline.
> And increasing min_free value also may not help much.
> Currently, in our case free memory never falls below 10MB, with 512MB RAM
> configuration.
> 

How about the performance as you reclaim so much memory?
(e.g. shrink page cache, use zram, ksm, compaction...)
When launching the same app next time, it may be slow, right?

How about use cgroup to manage the apps, but I don't know how to do the detail.

Thanks,
Xishi Qiu

> 
> 



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