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Date: Tue, 5 Jan 2010 20:20:56 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Peter Zijlstra <peterz@infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, cl@linux-foundation.org, "hugh.dickins" <hugh.dickins@tiscali.co.uk>, Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>
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On Wed, 6 Jan 2010, KAMEZAWA Hiroyuki wrote:
> > 
> > Of course, your other load with MADV_DONTNEED seems to be horrible, and 
> > has some nasty spinlock issues, but that looks like a separate deal (I 
> > assume that load is just very hard on the pgtable lock).
> 
> It's zone->lock, I guess. My test program avoids pgtable lock problem.

Yeah, I should have looked more at your callchain. That's nasty. Much 
worse than the per-mm lock. I thought the page buffering would avoid the 
zone lock becoming a huge problem, but clearly not in this case.

		Linus

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