From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f71.google.com (mail-pa0-f71.google.com [209.85.220.71]) by kanga.kvack.org (Postfix) with ESMTP id D49966B0038 for ; Mon, 12 Sep 2016 01:24:29 -0400 (EDT) Received: by mail-pa0-f71.google.com with SMTP id ex14so166038666pac.0 for ; Sun, 11 Sep 2016 22:24:29 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id cm7si18877917pad.48.2016.09.11.22.24.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 11 Sep 2016 22:24:26 -0700 (PDT) Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id u8C5NC2j057845 for ; Mon, 12 Sep 2016 01:24:25 -0400 Received: from e23smtp03.au.ibm.com (e23smtp03.au.ibm.com [202.81.31.145]) by mx0a-001b2d01.pphosted.com with ESMTP id 25ceawwnnr-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 12 Sep 2016 01:24:25 -0400 Received: from localhost by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 12 Sep 2016 15:24:22 +1000 Received: from d23relay07.au.ibm.com (d23relay07.au.ibm.com [9.190.26.37]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id B220D3578057 for ; Mon, 12 Sep 2016 15:24:19 +1000 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u8C5OJjj6553924 for ; Mon, 12 Sep 2016 15:24:19 +1000 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u8C5OJ3u017520 for ; Mon, 12 Sep 2016 15:24:19 +1000 Date: Mon, 12 Sep 2016 10:54:17 +0530 From: Anshuman Khandual MIME-Version: 1.0 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 Message-Id: <57D63C01.9090309@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Anshuman Khandual Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Dave Hansen 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. -- 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