linux-kernel - Re: [PATCH v2 00/18] Support non-lru page migration

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Date:	Mon, 28 Mar 2016 14:08:41 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	jlayton@...chiereds.net, bfields@...ldses.org,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, koct9i@...il.com,
	aquini@...hat.com, virtualization@...ts.linux-foundation.org,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Rik van Riel <riel@...hat.com>, rknize@...orola.com,
	Gioh Kim <gi-oh.kim@...fitbricks.com>,
	Sangseok Lee <sangseok.lee@....com>,
	Chan Gyun Jeong <chan.jeong@....com>,
	Al Viro <viro@...IV.linux.org.uk>,
	YiPing Xu <xuyiping@...ilicon.com>
Subject: Re: [PATCH v2 00/18] Support non-lru page migration

Hello Andrew,

On Mon, Mar 21, 2016 at 03:30:49PM +0900, Minchan Kim 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".
> 
> Originally, Gioh Kim tried to support this feature but he moved
> so I took over the work. But I took many code from his work and
> changed a little bit.
> Thanks, Gioh!
> 
> And I should mention Konstantin Khlebnikov. He really heped Gioh
> at that time so he should deserve to have many credit, too.
> Thanks, Konstantin!
> 
> This patchset consists of five parts
> 
> 1. clean up migration
>   mm: use put_page to free page instead of putback_lru_page
> 
> 2. zsmalloc clean-up for preparing page migration
>   zsmalloc: use first_page rather than page
>   zsmalloc: clean up many BUG_ON
>   zsmalloc: reordering function parameter
>   zsmalloc: remove unused pool param in obj_free
>   zsmalloc: keep max_object in size_class
>   zsmalloc: squeeze inuse into page->mapping
>   zsmalloc: squeeze freelist into page->mapping
>   zsmalloc: move struct zs_meta from mapping to freelist
>   zsmalloc: factor page chain functionality out
>   zsmalloc: separate free_zspage from putback_zspage
>   zsmalloc: zs_compact refactoring

In this series, [2-5] are clean up regardless of goal of the patchset
so it could be merged independently.
I want to reduce patchset size in next post.
If anyone are not against, could you merge cleanup patchset?

   zsmalloc: use first_page rather than page
   zsmalloc: clean up many BUG_ON
   zsmalloc: reordering function parameter
   zsmalloc: remove unused pool param in obj_free

Thanks.