linux-kernel - Re: [PATCH -V2 0/9] memcg: add HugeTLB resource tracking

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Date:	Tue, 6 Mar 2012 13:38:09 +1100
From:	David Gibson <dwg@....ibm.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	mgorman@...e.de, kamezawa.hiroyu@...fujitsu.com, dhillf@...il.com,
	aarcange@...hat.com, mhocko@...e.cz, hannes@...xchg.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH -V2 0/9] memcg: add HugeTLB resource tracking

On Sun, Mar 04, 2012 at 11:39:23PM +0530, Aneesh Kumar K.V wrote:
> On Fri, 2 Mar 2012 14:28:53 +1100, David Gibson <dwg@....ibm.com> wrote:
> > On Thu, Mar 01, 2012 at 02:40:29PM -0800, Andrew Morton wrote:
> > > On Thu,  1 Mar 2012 14:46:11 +0530
> > > "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> wrote:
> > > 
> > > > This patchset implements a memory controller extension to control
> > > > HugeTLB allocations. It is similar to the existing hugetlb quota
> > > > support in that, the limit is enforced at mmap(2) time and not at
> > > > fault time. HugeTLB's quota mechanism limits the number of huge pages
> > > > that can allocated per superblock.
> > > > 
> > > > For shared mappings we track the regions mapped by a task along with the
> > > > memcg. We keep the memory controller charged even after the task
> > > > that did mmap(2) exits. Uncharge happens during truncate. For Private
> > > > mappings we charge and uncharge from the current task cgroup.
> > > 
> > > I haven't begin to get my head around this yet, but I'd like to draw
> > > your attention to https://lkml.org/lkml/2012/2/15/548.  That fix has
> > > been hanging around for a while, but I haven't done anything with it
> > > yet because I don't like its additional blurring of the separation
> > > between hugetlb core code and hugetlbfs.  I want to find time to sit
> > > down and see if the fix can be better architected but haven't got
> > > around to that yet.
> > 
> > So.. that version of the fix I specifically rebuilt to address your
> > concerns about that blurring - in fact I think it reduces the current
> > layer blurring.  I haven't had any reply - what problems do see it as
> > still having?
> 
> https://lkml.org/lkml/2012/2/16/179 ?

Ah.  Missed that reply somehow.  Odd.  Replied now and I'll respin
accordingly.

> That is a serious issue isn't it ?

Yes, it is.  And it's been around for a long, long time.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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