From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1755863AbcILSNt (ORCPT <rfc822;w@1wt.eu>);
        Mon, 12 Sep 2016 14:13:49 -0400
Received: from mail-pa0-f46.google.com ([209.85.220.46]:33352 "EHLO
        mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1755723AbcILSNq (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 12 Sep 2016 14:13:46 -0400
Date: Mon, 12 Sep 2016 11:13:43 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
X-X-Sender: rientjes@chino.kir.corp.google.com
To: Anshuman Khandual <khandual@linux.vnet.ibm.com>
cc: Dave Hansen <dave.hansen@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: [PATCH V4] mm: Add sysfs interface to dump each node's zonelist
 information
In-Reply-To: <57D63CB2.8070003@linux.vnet.ibm.com>
Message-ID: <alpine.DEB.2.10.1609121106500.39030@chino.kir.corp.google.com>
References: <1473150666-3875-1-git-send-email-khandual@linux.vnet.ibm.com> <1473302818-23974-1-git-send-email-khandual@linux.vnet.ibm.com> <57D1C914.9090403@intel.com> <57D63CB2.8070003@linux.vnet.ibm.com>
User-Agent: Alpine 2.10 (DEB 1266 2009-07-14)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, 12 Sep 2016, Anshuman Khandual wrote:

> >> > 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.
> > Doesn't this violate the "one value per file" sysfs rule?  Does it
> > belong in debugfs instead?
> 
> Yeah sure. Will make it a debugfs interface.
> 

So the intended reader of this file is running as root?

> > I also really question the need to dump kernel addresses out, filtered 
> > or not.  What's the point?
> 
> Hmm, thought it to be an additional information. But yes its additional
> and can be dropped.
> 

I'm questioning if this information can be inferred from information 
already in /proc/zoneinfo and sysfs.  We know the no-fallback zonelist is 
going to include the local node, and we know the other zonelists are 
either node ordered or zone ordered (or do we need to extend 
vm.numa_zonelist_order for default?).  I may have missed what new 
knowledge this interface is imparting on us.