Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759708AbZKFTrT (ORCPT ); Fri, 6 Nov 2009 14:47:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759682AbZKFTrS (ORCPT ); Fri, 6 Nov 2009 14:47:18 -0500 Received: from smtp.ultrahosting.com ([74.213.175.253]:35944 "EHLO smtp.ultrahosting.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1757783AbZKFTrS (ORCPT ); Fri, 6 Nov 2009 14:47:18 -0500 Date: Fri, 6 Nov 2009 14:45:58 -0500 (EST) From: Christoph Lameter X-X-Sender: cl@V090114053VZO-1 To: Andi Kleen cc: npiggin@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Tejun Heo , Ingo Molnar , KAMEZAWA Hiroyuki , "hugh.dickins@tiscali.co.uk" Subject: Re: [RFC MM] mmap_sem scaling: only scan cpus used by an mm In-Reply-To: <20091106191448.GD819@basil.fritz.box> Message-ID: References: <87r5sc7kst.fsf@basil.nowhere.org> <20091106073946.GV31511@one.firstfloor.org> <20091106191448.GD819@basil.fritz.box> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 781 Lines: 19 On Fri, 6 Nov 2009, Andi Kleen wrote: > On Fri, Nov 06, 2009 at 01:53:35PM -0500, Christoph Lameter wrote: > > One way to reduce the cost of the writer lock is to track the cpus used > > and loop over the processors in that bitmap. > > Can't you use the same mask as is used for TLB flushing? They are clearing the cpus that are no longer in use. We could use the same mask if we would transfer the counters but for that we would need to make sure that no concurrent user of the counters is out there. Probably too expensive to do. -- 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/