Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754036AbZCIUNm (ORCPT ); Mon, 9 Mar 2009 16:13:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752308AbZCIUNd (ORCPT ); Mon, 9 Mar 2009 16:13:33 -0400 Received: from smtp-out.google.com ([216.239.45.13]:61277 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751670AbZCIUNc (ORCPT ); Mon, 9 Mar 2009 16:13:32 -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=MRQA/6yFPdl18Rp/X/dnwTsgllwpAC1OmmXgHlCBq1D0lVu/xvvh9UC4O++iJR97g uyw4BBs+84ri6xCXH/vdw== Date: Mon, 9 Mar 2009 13:13:06 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Christoph Lameter cc: 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: Message-ID: References: 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: 1153 Lines: 30 On Mon, 9 Mar 2009, Christoph Lameter wrote: > Again these are fastpath modifications. > The nature of the change requires the logic to be placed in the fastpath to determine whether a cpu slab's node is allowed by the allocating task's cpuset. You have previously stated that you would prefer that this feature be tunable from userspace. This patch adds the `memory_slab_hardwall' cpuset flag which defaults to off. > Scanning the partial list for matching nodes is an expensive operation. > It depends on how long you scan for a matching node, but again: this should be assumed by the user if the option has been enabled. > Adding RCU into the fast paths is also another big worry. > This could be mitigated by adding a PF_SLAB_HARDWALL flag similiar to PF_SPREAD_PAGE and PF_SPREAD_SLAB. I'd prefer not to add additional cpuset-specific task flags, but this would address your concern. -- 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/