Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759313AbZLQIln (ORCPT ); Thu, 17 Dec 2009 03:41:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751525AbZLQIll (ORCPT ); Thu, 17 Dec 2009 03:41:41 -0500 Received: from one.firstfloor.org ([213.235.205.2]:49997 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751262AbZLQIlk (ORCPT ); Thu, 17 Dec 2009 03:41:40 -0500 Date: Thu, 17 Dec 2009 09:41:39 +0100 From: Andi Kleen To: Peter Zijlstra Cc: Christoph Lameter , Andi Kleen , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "mingo@elte.hu" , minchan.kim@gmail.com Subject: Re: [mm][RFC][PATCH 0/11] mm accessor updates. Message-ID: <20091217084138.GB9804@basil.fritz.box> References: <20091216120011.3eecfe79.kamezawa.hiroyu@jp.fujitsu.com> <20091216101107.GA15031@basil.fritz.box> <20091216191312.f4655dac.kamezawa.hiroyu@jp.fujitsu.com> <20091216102806.GC15031@basil.fritz.box> <20091216193109.778b881b.kamezawa.hiroyu@jp.fujitsu.com> <20091216104951.GD15031@basil.fritz.box> <20091216201218.42ff7f05.kamezawa.hiroyu@jp.fujitsu.com> <20091216113158.GE15031@basil.fritz.box> <1261004515.21028.510.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1261004515.21028.510.camel@laptop> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1568 Lines: 39 On Thu, Dec 17, 2009 at 12:01:55AM +0100, Peter Zijlstra wrote: > On Wed, 2009-12-16 at 10:27 -0600, Christoph Lameter wrote: > > On Wed, 16 Dec 2009, Andi Kleen wrote: > > > > > > Do you have alternative recommendation rather than wrapping all accesses by > > > > special functions ? > > > > > > Work out what changes need to be done for ranged mmap locks and do them all > > > in one pass. > > > > Locking ranges is already possible through the split ptlock and > > could be enhanced through placing locks in the vma structures. > > > > That does nothing solve the basic locking issues of mmap_sem. We need > > Kame-sans abstraction layer. A vma based lock or a ptlock still needs to > > ensure that the mm struct does not vanish while the lock is held. > > It should, you shouldn't be able to remove a mm while there's still > vma's around, and you shouldn't be able to remove a vma when there's > still pagetables around. And if you rcu-free all of them you're stable > enough for lots of speculative behaviour. Yes, the existing reference counts are probably sufficient for all that. Still need list stability. > As for per-vma locks, those are pretty much useless too, there's plenty > applications doing lots of work on a few very large vmas. True. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/