linux-kernel - Re: [PATCH] mm: do not use page

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Message-ID: <4FD9433C.4060503@kernel.org>
Date:	Thu, 14 Jun 2012 10:49:48 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Andrea Arcangeli <aarcange@...hat.com>
CC:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH] mm: do not use page_count without a page pin

On 06/14/2012 10:21 AM, Andrea Arcangeli wrote:

> On Tue, Jun 12, 2012 at 07:49:34AM +0900, Minchan Kim wrote:
>> If THP page isn't LRU and it's still PageTransHuge, I think it's rather rare and
>> although it happens, it means migration/reclaimer is about to split or isolate/putback
>> so it ends up making THP page movable pages.
>>
>> IMHO, it would be better to account it by movable pages.
>> What do you think about it?
> 
> Agreed. Besides THP don't fragment pageblocks. It was just about
> speeding up the scanning the same way it happens with the pagebuddy
> check, but probably not worth it because we're in a racy area here not
> holding locks. pagebuddy is safe because the zone lock is hold, or
> it'd run in the same problem.


Yeb. zone lock is already hold so pagebuddy check is safe but THP still in a racy so let's leave it as it is.
If you don't have concern about this patch any more, could you add Acked-by in my latest patch for Andrew
to pick up? Although you have a concern, let's make it as separate patch because it's optimization patch and 
other patch is pending by this.

Thanks, Andrea.

-- 
Kind regards,
Minchan Kim
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