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Date: Tue, 3 Nov 2009 11:55:43 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, Andi Kleen <andi@firstfloor.org>,
       linux-mm@kvack.org, Marcelo Tosatti <mtosatti@redhat.com>,
       Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>,
       Izik Eidus <ieidus@redhat.com>,
       Hugh Dickins <hugh.dickins@tiscali.co.uk>,
       Nick Piggin <npiggin@suse.de>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Subject: Re: RFC: Transparent Hugepage support
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On Fri, Oct 30, 2009 at 09:40:37AM +0900, KAMEZAWA Hiroyuki wrote:
> Ah, please keep CONFIG_TRANSPARENT_HUGEPAGE for a while.
> Now, memcg don't handle hugetlbfs because it's special and cannot be freed by
> the kernel, only users can free it. But this new transparent-hugepage seems to
> be designed as that the kernel can free it for memory reclaiming.
> So, I'd like to handle this in memcg transparently.
> 
> But it seems I need several changes to support this new rule.
> I'm glad if this new huge page depends on !CONFIG_CGROUP_MEM_RES_CTRL for a
> while.

Yeah the accounting (not just memcg) should be checked.. I didn't pay
too much attention to stats at this point.

But we want to fix it fast instead of making the two options mutually
exclusive.. Where are the pages de-accounted when they are freed?
Accounting seems to require just two one liners
calling mem_cgroup_newpage_charge.