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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: David Rientjes <rientjes@google.com>
Subject: Re: [resend][PATCH] mm: Restore zone->all_unreclaimable to independence word
Cc: kosaki.motohiro@jp.fujitsu.com, LKML <linux-kernel@vger.kernel.org>,
       linux-mm <linux-mm@kvack.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Minchan Kim <minchan.kim@gmail.com>,
       Wu Fengguang <fengguang.wu@intel.com>, Huang Shijie <shijie8@gmail.com>
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Date: Thu, 14 Jan 2010 16:14:10 +0900 (JST)
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> On Thu, 14 Jan 2010, KOSAKI Motohiro wrote:
> 
> > commit e815af95 (change all_unreclaimable zone member to flags) chage
> > all_unreclaimable member to bit flag. but It have undesireble side
> > effect.
> > free_one_page() is one of most hot path in linux kernel and increasing
> > atomic ops in it can reduce kernel performance a bit.
> > 
> > Thus, this patch revert such commit partially. at least
> > all_unreclaimable shouldn't share memory word with other zone flags.
> > 
> 
> I still think you need to quantify this; saying you don't have a large 
> enough of a machine that will benefit from it isn't really a rationale for 
> the lack of any data supporting your claim.  We should be basing VM 
> changes on data, not on speculation that there's a measurable impact 
> here.
> 
> Perhaps you could ask a colleague or another hacker to run a benchmark for 
> you so that the changelog is complete?

ok, fair. although I dislike current unnecessary atomic-ops.
I'll pending this patch until get good data.

thanks.