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

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Message-ID: <1262884960.4049.106.camel@laptop>
Date:	Thu, 07 Jan 2010 18:22:40 +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 08:19 -0800, Linus Torvalds wrote:
> 
> So now some paths are indeed holding it for writing (or need to wait for 
> it to become writable). And the fairness of rwsems quite possibly then 
> impacts throughput a _lot_.. 

Right, supposing we can make this speculative fault stuff work, then we
can basically reduce the mmap_sem usage in fault to:

  - allocating new page tables
  - extending the growable vmas

And do everything else without holding it, including zeroing and IO.



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