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

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Date:	Thu, 07 Jan 2010 19:00:07 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>,
	"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 Thu, 2010-01-07 at 09:49 -0800, Linus Torvalds wrote:
> 
> The thing is, I can pretty much _guarantee_ that the speculative page 
> fault is going to end up doing a lot of nasty stuff that still needs 
> almost-global locking, and it's likely to be more complicated and slower 
> for the single-threaded case (you end up needing refcounts, a new "local" 
> lock or something).

Well, with that sync_vma() thing I posted the other day all the
speculative page fault needs is a write to current->fault_vma, the ptl
and an O(nr_threads) loop on unmap() for file vmas -- aside from writing
the pte itself of course.




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