linux-kernel - Re: [mm][RFC][PATCH 0/11] mm accessor updates.

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Date:	Fri, 18 Dec 2009 06:17:54 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.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>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	minchan.kim@...il.com
Subject: Re: [mm][RFC][PATCH 0/11] mm accessor updates.


* Christoph Lameter <cl@...ux-foundation.org> wrote:

> On Thu, 17 Dec 2009, Peter Zijlstra wrote:
> 
> > > That is why I think that the accessors are a good first step.
> >
> > They're not, they're daft, they operate on a global resource mm_struct, 
> > that's the whole problem, giving it a different name isn't going to solve 
> > anything.
> 
> It is not about naming. The accessors hide the locking mechanism for 
> mmap_sem. Then you can change the locking in a central place.
> 
> The locking may even become configurable later. Maybe an embedded solution 
> will want the existing scheme but dual quad socket may want a distributed 
> reference counter to avoid bouncing cachelines on faults.

Hiding the locking is pretty much the worst design decision one can make.

	Ingo
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