From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751243AbdBAGqb (ORCPT ); Wed, 1 Feb 2017 01:46:31 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:52060 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751004AbdBAGqa (ORCPT ); Wed, 1 Feb 2017 01:46:30 -0500 Subject: Re: [RFC V2 03/12] mm: Change generic FALLBACK zonelist creation process To: John Hubbard , Dave Hansen , Anshuman Khandual , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20170130033602.12275-1-khandual@linux.vnet.ibm.com> <20170130033602.12275-4-khandual@linux.vnet.ibm.com> <07bd439c-6270-b219-227b-4079d36a2788@intel.com> <434aa74c-e917-490e-85ab-8c67b1a82d95@linux.vnet.ibm.com> <79bfd849-8e6c-2f6d-0acf-4256a4137526@nvidia.com> Cc: mhocko@suse.com, vbabka@suse.cz, mgorman@suse.de, minchan@kernel.org, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, srikar@linux.vnet.ibm.com, haren@linux.vnet.ibm.com, jglisse@redhat.com, dan.j.williams@intel.com From: Anshuman Khandual Date: Wed, 1 Feb 2017 12:16:16 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <79bfd849-8e6c-2f6d-0acf-4256a4137526@nvidia.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17020106-0008-0000-0000-00000521A46E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17020106-0009-0000-0000-00001327BDC4 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-31_12:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702010066 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/31/2017 12:55 PM, John Hubbard wrote: > On 01/30/2017 05:57 PM, Dave Hansen wrote: >> On 01/30/2017 05:36 PM, Anshuman Khandual wrote: >>>> Let's say we had a CDM node with 100x more RAM than the rest of the >>>> system and it was just as fast as the rest of the RAM. Would we still >>>> want it isolated like this? Or would we want a different policy? >>> >>> But then the other argument being, dont we want to keep this 100X more >>> memory isolated for some special purpose to be utilized by specific >>> applications ? >> >> I was thinking that in this case, we wouldn't even want to bother with >> having "system RAM" in the fallback lists. A device who got its memory >> usage off by 1% could start to starve the rest of the system. A sane >> policy in this case might be to isolate the "system RAM" from the >> device's. > > I also don't like having these policies hard-coded, and your 100x > example above helps clarify what can go wrong about it. It would be > nicer if, instead, we could better express the "distance" between nodes > (bandwidth, latency, relative to sysmem, perhaps), and let the NUMA > system figure out the Right Thing To Do. > > I realize that this is not quite possible with NUMA just yet, but I > wonder if that's a reasonable direction to go with this? That is complete overhaul of the NUMA representation in the kernel. What CDM attempts is to find a solution with existing NUMA framework and with as little code change as possible.