linux-kernel - Re: [PATCH V3 6/8] memcg: Don't account root_mem

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Date:	Wed, 9 Jan 2013 13:57:58 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Sha Zhengju <handai.szj@...il.com>
Cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	linux-mm@...ck.org, akpm@...ux-foundation.org,
	kamezawa.hiroyu@...fujitsu.com, gthelen@...gle.com,
	fengguang.wu@...el.com, glommer@...allels.com,
	Sha Zhengju <handai.szj@...bao.com>
Subject: Re: [PATCH V3 6/8] memcg: Don't account root_mem_cgroup page
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On Sat 05-01-13 18:52:12, Sha Zhengju wrote:
> On Wed, Jan 2, 2013 at 8:27 PM, Michal Hocko <mhocko@...e.cz> wrote:
> > On Wed 26-12-12 01:27:27, Sha Zhengju wrote:
[...]
> >> @@ -5396,18 +5406,70 @@ static inline void mem_cgroup_lru_names_not_uptodate(void)
> >>       BUILD_BUG_ON(ARRAY_SIZE(mem_cgroup_lru_names) != NR_LRU_LISTS);
> >>  }
> >>
> >> +long long root_memcg_local_stat(unsigned int i, long long val,
> >> +                                     long long nstat[])
> >
> > Function should be static
> > also
> > nstat parameter is ugly because this can be done by the caller
> > and also expecting that the caller already calculated val is not
> > nice (and undocumented). This approach is really hackish and error
> > prone. Why should we define a specific function rather than hooking into
> > mem_cgroup_read_stat and doing all the stuff there? I think that would
> > be much more maintainable.
> >
> 
> IMHO, hooking into mem_cgroup_read_stat may be also improper because
> of the for_each_mem_cgroup traversal. I prefer to make mem_cgroup_read_stat
> as the base func unit. But I'll repeal the function base on your opinion in next
> version.  Thanks for the advice!

Maybe my "do all the stuff there" was confusing. I didn't mean to
iterate through the hierarchy there. I just wanted to have
mem_cgroup_root is a special case and it uses global counters there.
-- 
Michal Hocko
SUSE Labs
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