linux-kernel - Re: [RFC][PATCH 6/8] mm: handle_speculative

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Date:	Tue, 5 Jan 2010 20:20:56 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Minchan Kim <minchan.kim@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, cl@...ux-foundation.org,
	"hugh.dickins" <hugh.dickins@...cali.co.uk>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()



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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