linux-kernel - Re: [RFC PATCH 0/4] mm: reclaim zbud pages on migration and compaction

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Date:	Tue, 06 Aug 2013 17:16:31 +0800
From:	Bob Liu <bob.liu@...cle.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
CC:	Seth Jennings <sjenning@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [RFC PATCH 0/4] mm: reclaim zbud pages on migration and compaction

On 08/06/2013 02:42 PM, Krzysztof Kozlowski wrote:
> Hi,
> 
> Currently zbud pages are not movable and they cannot be allocated from CMA
> region. These patches try to address the problem by:
> 1. Adding a new form of reclaim of zbud pages.
> 2. Reclaiming zbud pages during migration and compaction.
> 3. Allocating zbud pages with __GFP_RECLAIMABLE flag.
> 
> This reclaim process is different than zbud_reclaim_page(). It acts more
> like swapoff() by trying to unuse pages stored in zbud page and bring
> them back to memory. The standard zbud_reclaim_page() on the other hand
> tries to write them back.

I prefer to migrate zbud pages directly if it's possible than reclaiming
them during compaction.

> 
> One of patches introduces a new flag: PageZbud. This flag is used in
> isolate_migratepages_range() to grab zbud pages and pass them later
> for reclaim. Probably this could be replaced with something
> smarter than a flag used only in one case.
> Any ideas for a better solution are welcome.
> 
> This patch set is based on Linux 3.11-rc4.
> 
> TODOs:
> 1. Replace PageZbud flag with other solution.
> 
> Best regards,
> Krzysztof Kozlowski
> 
> 
> Krzysztof Kozlowski (4):
>   zbud: use page ref counter for zbud pages
>   mm: split code for unusing swap entries from try_to_unuse
>   mm: add zbud flag to page flags
>   mm: reclaim zbud pages on migration and compaction
> 
>  include/linux/page-flags.h |   12 ++
>  include/linux/swapfile.h   |    2 +
>  include/linux/zbud.h       |   11 +-
>  mm/compaction.c            |   20 ++-
>  mm/internal.h              |    1 +
>  mm/page_alloc.c            |    9 ++
>  mm/swapfile.c              |  354 +++++++++++++++++++++++---------------------
>  mm/zbud.c                  |  301 +++++++++++++++++++++++++------------
>  mm/zswap.c                 |   57 ++++++-
>  9 files changed, 499 insertions(+), 268 deletions(-)
> 

-- 
Regards,
-Bob
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