linux-kernel - Re: [RFC 5/8] compaction: remove active list counting

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Message-ID: <BANLkTi=bMm+iyO23+16FxK__V1-aM50zWQ@mail.gmail.com>
Date:	Sat, 30 Apr 2011 00:25:41 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Johannes Weiner <jweiner@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC 5/8] compaction: remove active list counting

On Thu, Apr 28, 2011 at 7:50 PM, Mel Gorman <mgorman@...e.de> wrote:
> On Wed, Apr 27, 2011 at 01:25:22AM +0900, Minchan Kim wrote:
>> acct_isolated of compaction uses page_lru_base_type which returns only
>> base type of LRU list so it never returns LRU_ACTIVE_ANON or LRU_ACTIVE_FILE.
>> So it's pointless to add lru[LRU_ACTIVE_[ANON|FILE]] to get sum.
>>
>> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>> Cc: Mel Gorman <mgorman@...e.de>
>> Cc: Rik van Riel <riel@...hat.com>
>> Cc: Andrea Arcangeli <aarcange@...hat.com>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>
> hmm, isolate_migratepages() is doing a linear scan of PFNs and is
> calling __isolate_lru_page(..ISOLATE_BOTH..). Using page_lru_base_type
> happens to work because we're only interested in the number of isolated
> pages and your patch still covers that. Using page_lru might be more
> accurate in terms of accountancy but does not seem necessary.

True.

>
> Adding a comment explaining why we account for it as inactive and why
> that's ok would be nice although I admit this is something I should have
> done when acct_isolated() was introduced.

When Kame pointed out comment, I wanted to avoid unnecessary comment
so decided changing it with page_lru although it adds overhead a
little bit. But Hannes, you and maybe Kame don't want it. I don't mind
adding comment.
Okay. fix it in next version.

Thanks.

-- 
Kind regards,
Minchan Kim
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