linux-kernel - Re: [RFC 0/4] enable migration of non-LRU pages

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Date:	Wed, 10 Jun 2015 10:08:13 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Minchan Kim <minchan@...nel.org>
CC:	jlayton@...chiereds.net, bfields@...ldses.org,
	akpm@...ux-foundation.org, vbabka@...e.cz, iamjoonsoo.kim@....com,
	mst@...hat.com, kirill@...temov.name, mgorman@...e.de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	virtualization@...ts.linux-foundation.org, gunho.lee@....com
Subject: Re: [RFC 0/4] enable migration of non-LRU pages



2015-06-10 오전 9:08에 Minchan Kim 이(가) 쓴 글:
> Hello Gioh,
>
> On Tue, Jun 02, 2015 at 04:27:40PM +0900, Gioh Kim wrote:
>> Hello,
>>
>> This series try to enable migration of non-LRU pages, such as driver's page.
>>
>> My ARM-based platform occured severe fragmentation problem after long-term
>> (several days) test. Sometimes even order-3 page allocation failed. It has
>> memory size 512MB ~ 1024MB. 30% ~ 40% memory is consumed for graphic processing
>> and 20~30 memory is reserved for zram.
>>
>> I found that many pages of GPU driver and zram are non-movable pages. So I
>> reported Minchan Kim, the maintainer of zram, and he made the internal
>> compaction logic of zram. And I made the internal compaction of GPU driver.
>>
>> They reduced some fragmentation but they are not enough effective.
>> They are activated by its own interface, /sys, so they are not cooperative
>> with kernel compaction. If there is too much fragmentation and kernel starts
>> to compaction, zram and GPU driver cannot work with the kernel compaction.
>>
>> The first this patch adds a generic isolate/migrate/putback callbacks for page
>> address-space. The zram and GPU, and any other modules can register
>> its own migration method. The kernel compaction can call the registered
>> migration when it works. Therefore all page in the system can be migrated
>> at once.
>>
>> The 2nd the generic migration callbacks are applied into balloon driver.
>> My gpu driver code is not open so I apply generic migration into balloon
>> to show how it works. I've tested it with qemu enabled by kvm like followings:
>> - turn on Ubuntu 14.04 with 1G memory on qemu.
>> - do kernel building
>> - after several seconds check more than 512MB is used with free command
>> - command "balloon 512" in qemu monitor
>> - check hundreds MB of pages are migrated
>>
>> Next kernel compaction code can call generic migration callbacks instead of
>> balloon driver interface.
>> Finally calling migration of balloon driver is removed.
>
> I didn't hava a time to review but it surely will help using zram with
> CMA as well as fragmentation of the system memory via making zram objects
> movable.

I know you are busy. I hope you make time for review.

>
> If it lands on mainline, I will work for zram object migration.
>
> Thanks!
>
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