linux-kernel - Re: [PATCH v3 03/10] Add additional isolation mode

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Date:	Mon, 13 Jun 2011 23:54:43 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH v3 03/10] Add additional isolation mode

On Sun, Jun 12, 2011 at 04:45:21PM +0200, Michal Hocko wrote:
> On Tue 07-06-11 23:38:16, Minchan Kim wrote:
> > There are some places to isolate lru page and I believe
> > users of isolate_lru_page will be growing.
> > The purpose of them is each different so part of isolated pages
> > should put back to LRU, again.
> > 
> > The problem is when we put back the page into LRU,
> > we lose LRU ordering and the page is inserted at head of LRU list.
> > It makes unnecessary LRU churning so that vm can evict working set pages
> > rather than idle pages.
> 
> I guess that, although this is true, it doesn't fit in with this patch
> very much because this patch doesn't fix this problem. It is a
> preparation for for further work. I would expect this description with
> the core patch that actlually handles this issue.

Okay.

> 
> > 
> > This patch adds new modes when we isolate page in LRU so we don't isolate pages
> > if we can't handle it. It could reduce LRU churning.
> > 
> > This patch doesn't change old behavior. It's just used by next patches.
> 
> It doesn't because there is not user of those flags but maybe it would
> be better to have those to see why it actually can reduce LRU
> isolations.

Yes. Mel already pointed it out.
I will merge patches in next version.
And I have a idea to reduce lru_lock Mel mentiond
So maybe I will include it in next version, too.
But, now I have no time to revise it :(

-- 
Kind regards,
Minchan Kim
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