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Date: Wed, 30 Mar 2016 16:11:41 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, jlayton@poochiereds.net,
        bfields@fieldses.org, Vlastimil Babka <vbabka@suse.cz>,
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        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Rik van Riel <riel@redhat.com>, rknize@motorola.com,
        Gioh Kim <gi-oh.kim@profitbricks.com>,
        Sangseok Lee <sangseok.lee@lge.com>,
        Chan Gyun Jeong <chan.jeong@lge.com>,
        Al Viro <viro@ZenIV.linux.org.uk>, YiPing Xu <xuyiping@hisilicon.com>
Subject: Re: [PATCH v3 00/16] Support non-lru page migration
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On Wed, 30 Mar 2016 16:11:59 +0900 Minchan Kim <minchan@kernel.org> wrote:

> Recently, I got many reports about perfermance degradation
> in embedded system(Android mobile phone, webOS TV and so on)
> and failed to fork easily.
> 
> The problem was fragmentation caused by zram and GPU driver
> pages. Their pages cannot be migrated so compaction cannot
> work well, either so reclaimer ends up shrinking all of working
> set pages. It made system very slow and even to fail to fork
> easily.
> 
> Other pain point is that they cannot work with CMA.
> Most of CMA memory space could be idle(ie, it could be used
> for movable pages unless driver is using) but if driver(i.e.,
> zram) cannot migrate his page, that memory space could be
> wasted. In our product which has big CMA memory, it reclaims
> zones too exccessively although there are lots of free space
> in CMA so system was very slow easily.
> 
> To solve these problem, this patch try to add facility to
> migrate non-lru pages via introducing new friend functions
> of migratepage in address_space_operation and new page flags.
> 
> 	(isolate_page, putback_page)
> 	(PG_movable, PG_isolated)
> 
> For details, please read description in
> "mm/compaction: support non-lru movable page migration".

OK, I grabbed all these.

I wonder about testing coverage during the -next period.  How many
people are likely to exercise these code paths in a serious way before
it all hits mainline?