linux-kernel - Re: -mm merge plans for 2.6.26 (memcgroup)

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Date:	Mon, 21 Apr 2008 09:30:59 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	Shi Weihua <shiwh@...fujitsu.com>, Mel Gorman <mel@....ul.ie>,
	linux-kernel@...r.kernel.org
Subject: Re: -mm merge plans for 2.6.26 (memcgroup)

On Mon, 21 Apr 2008 00:51:30 +0100 (BST)
Hugh Dickins <hugh@...itas.com> wrote:
> >  disable-the-memory-controller-by-default-v3.patch
> >  disable-the-memory-controller-by-default-v3-fix.patch
> 
> If those are to go in, then the sooner the better, yes.
> 
> But though I argued for cgroup_disable=memory (or some such),
> I think myself that taking it even further now (requiring an
> additional cgroup_enable=memory at boottime to get the memcg
> stuff you chose with CGROUP_MEM_RES_CTLR=y at build time) is
> confusing overkill, just messing around.
> 
> Others think differently.  A compromise would be to improve the
> helptext for CGROUP_MEM_RES_CTLR (some of it is presently nonsense,
> isn't it?  Certainly there's a significant overhead, but it's the
> 32-bit struct page not the 64-bit which then suffers from crossing
> cacheline boundaries).  Not much point in mentioning
> cgroup_disable=memory if those patches go in, but needs to say
> cgroup_enable=memory bootoption also needed.
> 
My concern around this is "default" action of cgroups may be different
from each otther. It's confusing...


> >  memcgroup-check-and-initialize-page-cgroup-in-memmap_init_zone.patch
> 
> No, it was a good find from Shi, but you were right to think the patch
> fishy, and Kame put in lots of work (thank you!) to identify the actual
> culprit: he and Mel are discussing what the actual fix should be; and
> we might want to choose a different fix for stable than for 2.6.26.
> 
> I think you should drop that memmap_init_zone patch: the cgroup
> pointer is not the only field we assume is zeroed, both flags and
> mapping can cause trouble if they were not originally zeroed.
> Re-zero the whole struct page?  No, far better to fix the
> root of the corruption, that Kame and Mel are working on.
> 
I'll test and repodt Mel's patch later. I think Shi's patch will be
unnecessary.

Thanks,
-Kame



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