From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 9C3826B0044 for ; Fri, 6 Nov 2009 02:39:50 -0500 (EST) Date: Fri, 6 Nov 2009 08:39:46 +0100 From: Andi Kleen Subject: Re: Subject: [RFC MM] mmap_sem scaling: Use mutex and percpu counter instead Message-ID: <20091106073946.GV31511@one.firstfloor.org> References: <87r5sc7kst.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: Andi Kleen , npiggin@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Tejun Heo , Ingo Molnar , KAMEZAWA Hiroyuki , "hugh.dickins@tiscali.co.uk" List-ID: On Thu, Nov 05, 2009 at 04:03:39PM -0500, Christoph Lameter wrote: > > For example it will definitely impact the AIM7 multi brk() issue > > or the mysql allocation case, which are all writer intensive. I assume > > doing a lot of mmaps/brks in parallel is not that uncommon. > > No its not that common. Page faults are much more common. The AIM7 seems > to be an artificial case? What does mysql do for allocation? If its brk() AIM7 is artificial yes, but I suspect similar problems (to a less extreme degree) are in other workloads. > related then simply going to larger increases may fix the issue?? For mysql it's mmap through malloc(). There has been some tuning in glibc for it. But I suspect it's a more general problem that will still need kernel improvements. > > > My thinking was more that we simply need per VMA locking or > > some other per larger address range locking. Unfortunately that > > needs changes in a lot of users that mess with the VMA lists > > (perhaps really needs some better abstractions for VMA list management > > first) > > We have range locking through the distribution of the ptl for systems with > more than 4 processors. One can use that today to lock ranges of the > address space. Yes but all the major calls still take mmap_sem, which is not ranged. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org