linux-kernel - Re: [patch 3/5] mm: try to distribute dirty pages fairly across zones

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Message-Id: <20111125100009.a87094fa.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 25 Nov 2011 10:00:09 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Michal Hocko <mhocko@...e.cz>,
	Christoph Hellwig <hch@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
	Shaohua Li <shaohua.li@...el.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 3/5] mm: try to distribute dirty pages fairly across
 zones

On Thu, 24 Nov 2011 14:11:55 +0100
Johannes Weiner <hannes@...xchg.org> wrote:

> On Thu, Nov 24, 2011 at 10:07:55AM +0900, KAMEZAWA Hiroyuki wrote:
			goto this_zone_full;
> > >  
> > >  		BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
> > >  		if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
> > 
> > This wil call 
> > 
> >                 if (NUMA_BUILD)
> >                         zlc_mark_zone_full(zonelist, z);
> > 
> > And this zone will be marked as full. 
> > 
> > IIUC, zlc_clear_zones_full() is called only when direct reclaim ends.
> > So, if no one calls direct-reclaim, 'full' mark may never be cleared
> > even when number of dirty pages goes down to safe level ?
> > I'm sorry if this is alread discussed.
> 
> It does not remember which zones are marked full for longer than a
> second - see zlc_setup() - and also ignores this information when an
> iteration over the zonelist with the cache enabled came up
> empty-handed.
> 
Ah, thank you for clarification.
I understand how zlc_active/did_zlc_setup/zlc_setup()...complicated ;)

Thanks,
-Kame

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