linux-kernel - Re: [PATCH 5/5] mm/cgroup: use N_MEMORY instead of N_HIGH

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Date:	Fri, 30 Aug 2013 16:29:14 +0800
From:	Jianguo Wu <wujianguo@...wei.com>
To:	Michal Hocko <mhocko@...e.cz>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>, <tj@...nel.org>,
	<laijs@...fujitsu.com>, <cgroups@...r.kernel.org>,
	<containers@...ts.linux-foundation.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, Wen Congyang <wency@...fujitsu.com>
Subject: Re: [PATCH 5/5] mm/cgroup: use N_MEMORY instead of N_HIGH_MEMORY

On 2013/8/30 15:41, Michal Hocko wrote:

> On Fri 30-08-13 11:44:57, Jianguo Wu wrote:
>> Since commit 8219fc48a(mm: node_states: introduce N_MEMORY),
> 
> But this very same commit also says:
> "
>     A.example 2) mm/page_cgroup.c use N_HIGH_MEMORY twice:
>     
>         One is in page_cgroup_init(void):
>                 for_each_node_state(nid, N_HIGH_MEMORY) {
>     
>         It means if the node have memory, we will allocate page_cgroup map for
>         the node. We should use N_MEMORY instead here to gaim more clearly.
>     
>         The second using is in alloc_page_cgroup():
>                 if (node_state(nid, N_HIGH_MEMORY))
>                         addr = vzalloc_node(size, nid);
>     
>         It means if the node has high or normal memory that can be allocated
>         from kernel. We should keep N_HIGH_MEMORY here, and it will be better
>         if the "any memory" semantic of N_HIGH_MEMORY is removed.
> "
> 
> Which to me sounds like N_HIGH_MEMORY should be kept here. To be honest,

Hi Michal,

You are right, here we need normal or high memory, but not movable memory,
so N_HIGH_MEMORY should be kept here, the same as other patches, please drop this series.

Thank you for your point out.

Thanks,
Jianguo Wu.

> the distinction is not entirely clear to me. It was supposed to make
> code cleaner but it apparently causes confusion.
> 
> It would also help if you CCed Lai Jiangshan who has introduced this
> distinction. CCed now.
> 
> I wasn't CCed on the rest of the series but if you do the same
> conversion, please make sure that this is not the case for others as
> well.
> 
>> we introduced N_MEMORY, now N_MEMORY stands for the nodes that has any memory,
>> and N_HIGH_MEMORY stands for the nodes that has normal or high memory.
>>
>> The code here need to handle with the nodes which have memory,
>> we should use N_MEMORY instead.
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
>> ---
>>  mm/page_cgroup.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
>> index 6d757e3..f6f7603 100644
>> --- a/mm/page_cgroup.c
>> +++ b/mm/page_cgroup.c
>> @@ -116,7 +116,7 @@ static void *__meminit alloc_page_cgroup(size_t size, int nid)
>>  		return addr;
>>  	}
>>  
>> -	if (node_state(nid, N_HIGH_MEMORY))
>> +	if (node_state(nid, N_MEMORY))
>>  		addr = vzalloc_node(size, nid);
>>  	else
>>  		addr = vzalloc(size);
>> -- 
>> 1.7.1
>>
>>
> 



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