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

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Message-Id: <20100105150932.ab2e6820.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 5 Jan 2010 15:09:32 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	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 Tue, 5 Jan 2010 15:09:47 +0900
Minchan Kim <minchan.kim@...il.com> wrote:
> My humble opinion is following as.
> 
> Couldn't we synchronize rcu in that cases(munmap, exit and so on)?
> It can delay munap and exit but it would be better than handling them by more
> complicated things, I think. And both cases aren't often cases so we
> can achieve advantage than disadvantage?
> 

In most case, a program is single threaded. And sychronize_rcu() in unmap path
just adds very big overhead.

Thanks,
-Kame

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