From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932585AbcILFY2 (ORCPT ); Mon, 12 Sep 2016 01:24:28 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36607 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751677AbcILFY1 (ORCPT ); Mon, 12 Sep 2016 01:24:27 -0400 X-IBM-Helo: d23dlp02.au.ibm.com X-IBM-MailFrom: khandual@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Mon, 12 Sep 2016 10:54:17 +0530 From: Anshuman Khandual User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Michal Hocko , Anshuman Khandual CC: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Dave Hansen Subject: Re: [PATCH V4] mm: Add sysfs interface to dump each node's zonelist information References: <1473150666-3875-1-git-send-email-khandual@linux.vnet.ibm.com> <1473302818-23974-1-git-send-email-khandual@linux.vnet.ibm.com> <20160909133648.GL4844@dhcp22.suse.cz> In-Reply-To: <20160909133648.GL4844@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16091205-1617-0000-0000-000001560AF5 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16091205-1618-0000-0000-000046AF77FE Message-Id: <57D63C01.9090309@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-09-12_03:,, 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=8.0.1-1609020000 definitions=main-1609120088 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/09/2016 07:06 PM, Michal Hocko wrote: > On Thu 08-09-16 08:16:58, Anshuman Khandual wrote: >> > Each individual node in the system has a ZONELIST_FALLBACK zonelist >> > and a ZONELIST_NOFALLBACK zonelist. These zonelists decide fallback >> > order of zones during memory allocations. Sometimes it helps to dump >> > these zonelists to see the priority order of various zones in them. >> > >> > Particularly platforms which support memory hotplug into previously >> > non existing zones (at boot), this interface helps in visualizing >> > which all zonelists of the system at what priority level, the new >> > hot added memory ends up in. POWER is such a platform where all the >> > memory detected during boot time remains with ZONE_DMA for good but >> > then hot plug process can actually get new memory into ZONE_MOVABLE. >> > So having a way to get the snapshot of the zonelists on the system >> > after memory or node hot[un]plug is desirable. This change adds one >> > new sysfs interface (/sys/devices/system/memory/system_zone_details) >> > which will fetch and dump this information. > I am still not sure I understand why this is helpful and who is the > consumer for this interface and how it will benefit from the > information. Dave (who doesn't seem to be on the CC list re-added) had > another objection that this breaks one-value-per-file rule for sysfs > files. It helps in understanding the relative priority of each memory zone of the system during various allocation scenarios. Its particularly helpful after hotplug/unplug of additional memory into previously non existing zone on a node. > > This all smells like a debugging feature to me and so it should go into > debugfs. Sure, will make it a debugfs interface.