From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vc0-f170.google.com (mail-vc0-f170.google.com [209.85.220.170]) by kanga.kvack.org (Postfix) with ESMTP id 99B236B0037 for ; Fri, 30 May 2014 09:50:59 -0400 (EDT) Received: by mail-vc0-f170.google.com with SMTP id la4so2113553vcb.29 for ; Fri, 30 May 2014 06:50:59 -0700 (PDT) Received: from qmta07.emeryville.ca.mail.comcast.net (qmta07.emeryville.ca.mail.comcast.net. [2001:558:fe2d:43:76:96:30:64]) by mx.google.com with ESMTP id uk3si3044544vec.102.2014.05.30.06.50.58 for ; Fri, 30 May 2014 06:50:59 -0700 (PDT) Date: Fri, 30 May 2014 08:50:56 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH] page_alloc: skip cpuset enforcement for lower zone allocations (v5) In-Reply-To: Message-ID: References: <20140523193706.GA22854@amt.cnet> <20140526185344.GA19976@amt.cnet> <53858A06.8080507@huawei.com> <20140528224324.GA1132@amt.cnet> <20140529184303.GA20571@amt.cnet> <20140529232819.GA29803@amt.cnet> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Marcelo Tosatti , Li Zefan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lai Jiangshan , Mel Gorman , Tejun Heo , Andrew Morton , Andi Kleen On Thu, 29 May 2014, David Rientjes wrote: > When I said that my point about mempolicies needs more thought, I wasn't > expecting that there would be no discussion -- at least _something_ that > would say why we don't care about the mempolicy case. Lets get Andi involved here too. > The motivation here is identical for both cpusets and mempolicies. What > is the significant difference between attaching a process to a cpuset > without access to lowmem and a process doing set_mempolicy(MPOL_BIND) > without access to lowmem? Is it because the process should know what it's > doing if it asks for a mempolicy that doesn't include lowmem? If so, is > the cpusets case different because the cpuset attacher isn't held to the > same standard? > > I'd argue that an application may never know if it needs to allocate > GFP_DMA32 or not since its a property of the hardware that its running on > and my driver may need to access lowmem while yours may not. I may even > configure CONFIG_ZONE_DMA=n and CONFIG_ZONE_DMA32=n because I know the > _hardware_ requirements of my platforms. Right. This is a hardware issue and the hardware is pretty messed up. And now one wants to use NUMA features? > If there is no difference, then why are we allowing the exception for > cpusets and not mempolicies? > > I really think you want to allow both cpusets and mempolicies. I'd like > to hear Christoph's thoughts on it as well, though. I said something elsewhere in the thread. -- 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