Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753950AbbHUGci (ORCPT <rfc822;w@1wt.eu>);
	Fri, 21 Aug 2015 02:32:38 -0400
Received: from mail-wi0-f177.google.com ([209.85.212.177]:33861 "EHLO
	mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753159AbbHUGcg (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 21 Aug 2015 02:32:36 -0400
Date: Fri, 21 Aug 2015 08:32:33 +0200
From: Michal Hocko <mhocko@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        =?iso-8859-1?Q?J=F6rn?= Engel <joern@purestorage.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Naoya Horiguchi <nao.horiguchi@gmail.com>
Subject: Re: [PATCH v5 2/2] mm: hugetlb: proc: add HugetlbPages field to
 /proc/PID/status
Message-ID: <20150821063233.GB23723@dhcp22.suse.cz>
References: <20150812000336.GB32192@hori1.linux.bs1.fc.nec.co.jp>
 <1440059182-19798-1-git-send-email-n-horiguchi@ah.jp.nec.com>
 <1440059182-19798-3-git-send-email-n-horiguchi@ah.jp.nec.com>
 <20150820110004.GB4632@dhcp22.suse.cz>
 <alpine.DEB.2.10.1508201249010.27169@chino.kir.corp.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.10.1508201249010.27169@chino.kir.corp.google.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1554
Lines: 36

On Thu 20-08-15 12:49:59, David Rientjes wrote:
> On Thu, 20 Aug 2015, Michal Hocko wrote:
> 
> > On Thu 20-08-15 08:26:27, Naoya Horiguchi wrote:
> > > Currently there's no easy way to get per-process usage of hugetlb pages,
> > 
> > Is this really the case after your previous patch? You have both 
> > HugetlbPages and KernelPageSize which should be sufficient no?
> > 
> > Reading a single file is, of course, easier but is it really worth the
> > additional code? I haven't really looked at the patch so I might be
> > missing something but what would be an advantage over reading
> > /proc/<pid>/smaps and extracting the information from there?
> > 
> 
> /proc/pid/smaps requires root, /proc/pid/status doesn't.

Both mmotm and linus tree have
        REG("smaps",      S_IRUGO, proc_pid_smaps_operations),

and opening the file requires PTRACE_MODE_READ. So I do not see any
requirement for root here. Or did you mean that you need root to examine
all processes? That would be true but I am wondering why would be a regular
user interested in this break out numbers. Hugetlb management sounds
pretty much like an administrative or very specialized thing.

>From my understanding of the discussion there is no usecase to have this
information world readable. Is this correct?
-- 
Michal Hocko
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/