Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754020AbZCJCBz (ORCPT ); Mon, 9 Mar 2009 22:01:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752046AbZCJCBp (ORCPT ); Mon, 9 Mar 2009 22:01:45 -0400 Received: from smtp-out.google.com ([216.239.33.17]:49968 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223AbZCJCBo (ORCPT ); Mon, 9 Mar 2009 22:01:44 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id: references:user-agent:mime-version:content-type:x-system-of-record; b=gmlwh1FB5fAlfSaTSMwtDQNSi9WJKQmyvypUB5TKeR1tppz6Th5zZoKSsca/9PAZO YRPMNwdwXjaUFKTzVG9jA== Date: Mon, 9 Mar 2009 19:01:18 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: KOSAKI Motohiro cc: Christoph Lameter , Andrew Morton , Pekka Enberg , Matt Mackall , Paul Menage , Randy Dunlap , linux-kernel@vger.kernel.org Subject: Re: [patch -mm] cpusets: add memory_slab_hardwall flag In-Reply-To: <20090310102926.A47E.A69D9226@jp.fujitsu.com> Message-ID: References: <20090310102926.A47E.A69D9226@jp.fujitsu.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1328 Lines: 33 On Tue, 10 Mar 2009, KOSAKI Motohiro wrote: > That's pointless. > Again, any fastpath modification should have reasonable reason. > We are looking for your explanation. > The fastpath modification simply checks if the hardwall bit is set in the allocating task's cpuset flags. If it's disabled, there is no additional overhead. This requirement was mandated during the first review of the patch by Christoph, who requested that it be configurable. Before that it was possible to simply check if the global `number_of_cpusets' count was > 1. If not, cpuset_node_allowed_hardwall() would always return true. If the system had more than one cpuset, it would have reduced to checking return in_interrupt() || (gfp_mask & __GFP_THISNODE) || node_isset(node, current->mems_allowed); As I already mentioned, if fastpath optimization is your only concern, that we could simply add PF_SLAB_HARDWALL task flags that would simply make this return current->flags & PF_SLAB_HARDWALL; So the fastpath cost can be mitigated at the expense of an additional task flag. -- 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/