linux-kernel - Re: [PATCH] memcg: fix hotplugged memory zone oops

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Message-ID: <alpine.LNX.2.00.1211021626150.11106@eggly.anvils>
Date:	Fri, 2 Nov 2012 16:31:18 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Michal Hocko <mhocko@...e.cz>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Wen Congyang <wency@...fujitsu.com>,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	linux-mm@...ck.org, Jiang Liu <liuj97@...il.com>,
	bsingharora@...il.com,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	paul.gortmaker@...driver.com, Tang Chen <tangchen@...fujitsu.com>
Subject: Re: [PATCH] memcg: fix hotplugged memory zone oops

On Fri, 2 Nov 2012, Michal Hocko wrote:
> 
> OK, it adds "an overhead" also when there is no hotadd going on but this
> is just one additional mem access&cmp&je so it shouldn't be noticable
> (lruvec->zone is used most of the time later so it not a pointless
> load).

I think so too.

> It is also easier to backport for stable.

Yes.

> But is there any reason to fix it later properly in the hotadd hook?

I don't know.  Not everybody liked it fixed this way: it's not
unreasonable to see this as a quick hack rather than the right fix.

I was expecting objectors to post alternative hotadd hook patches,
then we could compare and decide.  That didn't happen; but we can
certainly look to taking out these lines later if something we
agree is better comes along.  Not high on anyone's agenda, I think.

> 
> Anyway
> Acked-by: Michal Hocko <mhocko@...e.cz>

Thanks,
Hugh
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