Message-ID: <4FE7E7FA.80702@jp.fujitsu.com>
Date: Mon, 25 Jun 2012 13:24:26 +0900
From: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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To: Johannes Weiner <hannes@cmpxchg.org>
CC: Wanpeng Li <liwp.linux@gmail.com>, linux-mm@kvack.org,
        Michal Hocko <mhocko@suse.cz>, Balbir Singh <bsingharora@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mel@csn.ul.ie>,
        Minchan Kim <minchan@kernel.org>, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, Gavin Shan <shangw@linux.vnet.ibm.com>
Subject: Re: [PATCH 1/6] memcg: replace unsigned long by u64 to avoid overflow
References: <1340432134-5178-1-git-send-email-liwp.linux@gmail.com> <20120623081514.GJ27816@cmpxchg.org> <20120623090339.GA6184@kernel> <20120623092654.GL27816@cmpxchg.org>
In-Reply-To: <20120623092654.GL27816@cmpxchg.org>
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(2012/06/23 18:26), Johannes Weiner wrote:
> On Sat, Jun 23, 2012 at 05:03:39PM +0800, Wanpeng Li wrote:
>> On Sat, Jun 23, 2012 at 10:15:14AM +0200, Johannes Weiner wrote:
>>> On Sat, Jun 23, 2012 at 02:15:34PM +0800, Wanpeng Li wrote:
>>>> From: Wanpeng Li <liwp@linux.vnet.ibm.com>
>>>>
>>>> Since the return value variable in mem_cgroup_zone_nr_lru_pages and
>>>> mem_cgroup_node_nr_lru_pages functions are u64, so replace the return
>>>> value of funtions by u64 to avoid overflow.
>>>
>>> I wonder what 16 TB of memory must think running on a 32-bit kernel...
>>> "What is this, an address space for ants?"
>>
>> Hi Johannes,
>>
>> You mean change all u64 in memcg to unsigned long? or something I
>> miss....
>
> Not _all_ of them, we have some that count bytes.  But those counting
> pages should probably be ulong, yes.
>
> I think Kame added the ones that you wanted to adjust the surroundings
> for in particular, so let's ask him.  Kame?
>

I've been using 'unsigned long' for the number of pages and 'u64' for the number of
bytes. I think it's enough and it should be. I don't have any reason to use u64 for
the number of pages on 32bit archs.
If 'bytes' are handled by 'unsigned long', please fix it.

BTW, zone_page_state()::/include/linux/vmstat.h returns 'unsigned long'.
If you want to change this in memcg, please change zone's ones first.

Thanks,
-Kame

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