Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932123AbaGKP7L (ORCPT ); Fri, 11 Jul 2014 11:59:11 -0400 Received: from qmta13.emeryville.ca.mail.comcast.net ([76.96.27.243]:46568 "EHLO qmta13.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753869AbaGKP7J (ORCPT ); Fri, 11 Jul 2014 11:59:09 -0400 Date: Fri, 11 Jul 2014 10:58:52 -0500 (CDT) From: Christoph Lameter To: Tejun Heo cc: Jiang Liu , Andrew Morton , Mel Gorman , David Rientjes , Mike Galbraith , Peter Zijlstra , "Rafael J . Wysocki" , Vladimir Davydov , Johannes Weiner , "Kirill A. Shutemov" , Rik van Riel , Wanpeng Li , Zhang Yanfei , Catalin Marinas , Jianyu Zhan , malc , Joonsoo Kim , Fabian Frederick , Tony Luck , linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC Patch V1 07/30] mm: Use cpu_to_mem()/numa_mem_id() to support memoryless node In-Reply-To: <20140711152156.GB29137@htj.dyndns.org> Message-ID: References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com> <1405064267-11678-8-git-send-email-jiang.liu@linux.intel.com> <20140711144205.GA27706@htj.dyndns.org> <20140711152156.GB29137@htj.dyndns.org> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Jul 2014, Tejun Heo wrote: > Hello, > > On Fri, Jul 11, 2014 at 10:13:57AM -0500, Christoph Lameter wrote: > > Allocators typically fall back but they wont in some cases if you say > > that you want memory from a particular node. A GFP_THISNODE would force a > > failure of the alloc. In other cases it should fall back. I am not sure > > that all allocations obey these conventions though. > > But, GFP_THISNODE + numa_mem_id() is identical to numa_node_id() + > nearest node with memory fallback. Is there any case where the user > would actually want to always fail if it's on the memless node? GFP_THISNODE allocatios must fail if there is no memory available on the node. No fallback allowed. If the allocator performs caching for a particular node (like SLAB) then the allocator *cannnot* accept memory from another node and the alloc via the page allocator must fail so that the allocator can then pick another node for keeping track of the allocations. > Even if that's the case, there's no reason to burden everyone with > this distinction. Most users just wanna say "I'm on this node. > Please allocate considering that". There's nothing wrong with using > numa_node_id() for that. Well yes that speaks for this patch. -- 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/