linux-kernel - Re: [PATCH v5 2/2] mm: hugetlb: proc: add HugetlbPages field to /proc/PID/status

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Message-ID: <20150821163033.GA4600@Sligo.logfs.org>
Date:	Fri, 21 Aug 2015 09:30:33 -0700
From:	Jörn Engel <joern@...estorage.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Mike Kravetz <mike.kravetz@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v5 2/2] mm: hugetlb: proc: add HugetlbPages field to
 /proc/PID/status

On Fri, Aug 21, 2015 at 08:53:21AM +0200, Michal Hocko wrote:
> On Thu 20-08-15 23:34:51, Naoya Horiguchi wrote:
> [...]
> > > 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?
> > 
> > My first idea was just "users should feel it useful", but permission as David
> > commented sounds a good technical reason to me.
> 
> 9 files changed, 112 insertions(+), 1 deletion(-)
> 
> is quite a lot especially when it touches hot paths like fork so it
> better should have a good usecase. I have already asked in the other
> email but is actually anybody requesting this? Nice to have is not
> a good justification IMO.

I need some way to judge the real rss of a process, including huge
pages.  No strong opinion on implementation details, but something is
clearly needed.

If you have processes with 99% huge pages, you are currently reduced to
guesswork.

Jörn

--
Journalism is printing what someone else does not want printed;
everything else is public relations.
-- George Orwell
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