Date: Wed, 13 Jun 2012 16:19:21 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@suse.cz>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH] mm: clean up __count_immobile_pages
Message-Id: <20120613161921.e791d469.akpm@linux-foundation.org>
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	<20120611144011.60fd76c8.akpm@linux-foundation.org>
	<4FD67E00.4040700@kernel.org>
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On Tue, 12 Jun 2012 08:23:44 +0900
Minchan Kim <minchan@kernel.org> wrote:

> On 06/12/2012 06:40 AM, Andrew Morton wrote:
> 
> > On Mon, 11 Jun 2012 11:07:22 +0900
> > Minchan Kim <minchan@kernel.org> wrote:
> > 
> >> __count_immobile_pages naming is rather awkward.
> >> This patch clean up the function and add comment.
> > 
> > This conflicts with
> > mm-compaction-handle-incorrect-migrate_unmovable-type-pageblocks.patch
> > and its fixes.
> 

It would be useful to Cc Bart when we're discussing his patch...

> I wanted to revert [1] and friends and merge again based on [2] and this patch.
> Because [1] has still bug I explained in [2]. If it is merged without [2], it simply can
> spread bug from one place(memory hotplug) to two place(memory hotplug and compaction).
> 
> We discussed real effectiveness of [1] because the patch is rather complicated than
> expectation. I don't want to add unnecessary maintain cost if it doesn't have proved benefit.
> 
> KOSAKI and me : doesn't want to merge without proving (https://lkml.org/lkml/2012/6/5/3)
> Mel: Pass the decision to CMA guys (https://lkml.org/lkml/2012/6/11/242)
> Rik: want to test it based on THP alloc ratio (https://lkml.org/lkml/2012/6/11/293)
> 
> I guess anyone has no sure for needing it, at least.
> 
> Even, [1] added new vmstat "compact_rescued_unmovable_blocks". 
> Why I firstly suggest is just for the proving the effectiveness easily and wanted to
> revert the vmstat later before merging mainline if we prove it.
> (But it seems that KOSAKI doesn't like it - https://lkml.org/lkml/2012/6/5/282)
> But now Bartlomiej want to maintain it permanently in vmstat.
> IMHO, it's not a good idea.
> Anyway, adding new vmstat part should be careful and get a agreement from mm guys.
> 
> [1] mm-compaction-handle-incorrect-migrate_unmovable-type-pageblocks.patch
> [2] [PATCH] mm: do not use page_count without a page pin

Right now I'm inclined to drop
mm-compaction-handle-incorrect-migrate_unmovable-type-pageblocks.patch
then sit back and let you guys hash out a new patch(set).

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