Date: Mon, 13 Dec 2010 08:58:55 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Simon Kirby <sim@hostway.ca>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Shaohua Li <shaohua.li@intel.com>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/6] mm: kswapd: Treat zone->all_unreclaimable in
 sleeping_prematurely similar to balance_pgdat()
Message-Id: <20101213085855.d0e907bd.kamezawa.hiroyu@jp.fujitsu.com>
In-Reply-To: <20101210105532.GM20133@csn.ul.ie>
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	<1291893500-12342-6-git-send-email-mel@csn.ul.ie>
	<20101210102337.8ff1fad2.kamezawa.hiroyu@jp.fujitsu.com>
	<20101210105532.GM20133@csn.ul.ie>
Organization: FUJITSU Co. LTD.
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On Fri, 10 Dec 2010 10:55:32 +0000
Mel Gorman <mel@csn.ul.ie> wrote:

> On Fri, Dec 10, 2010 at 10:23:37AM +0900, KAMEZAWA Hiroyuki wrote:
> > On Thu,  9 Dec 2010 11:18:19 +0000
> > Mel Gorman <mel@csn.ul.ie> wrote:
> > 
> > > After DEF_PRIORITY, balance_pgdat() considers all_unreclaimable zones to
> > > be balanced but sleeping_prematurely does not. This can force kswapd to
> > > stay awake longer than it should. This patch fixes it.
> > > 
> > > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> > 
> > Hmm, maybe the logic works well but I don't like very much.
> > 
> > How about adding below instead of pgdat->node_present_pages ?
> > 
> > static unsigned long required_balanced_pages(pgdat, classzone_idx)
> > {
> > 	unsigned long present = 0;
> > 
> > 	for_each_zone_in_node(zone, pgdat) {
> > 		if (zone->all_unreclaimable) /* Ignore unreclaimable zone at checking balance */
> > 			continue;
> > 		if (zone_idx(zone) > classzone_idx)
> > 			continue;
> > 		present = zone->present_pages;
> > 	}
> > 	return present;
> > }
> > 
> 
> I'm afraid I do not really understand. After your earlier comments,
> pgdat_balanced() now looks like
> 
> static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
>                                                 int classzone_idx)
> {
>         unsigned long present_pages = 0;
>         int i;
> 
>         for (i = 0; i <= classzone_idx; i++)
>                 present_pages += pgdat->node_zones[i].present_pages;
> 
>         return balanced_pages > (present_pages >> 2);
> }
> 
> so the classzone is being taken into account. I'm not sure what you're
> asking for it to be changed to. Maybe it'll be clearer after V4 comes
> out rebased on top of mmotm.
> 

Ah, this seems okay to me.

Thank you.
-Kame


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