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Date: Tue, 09 Apr 2013 00:05:54 +0800
From: Jiang Liu <liuj97@gmail.com>
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Subject: Re: [PATCH v4, part3 11/15] mm: use a dedicated lock to protect totalram_pages
 and zone->managed_pages
References: <1365256509-29024-1-git-send-email-jiang.liu@huawei.com> <1365256509-29024-12-git-send-email-jiang.liu@huawei.com> <5162C887.5070900@redhat.com>
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To: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jiang Liu <jiang.liu@huawei.com>, David Rientjes <rientjes@google.com>, Wen Congyang <wency@cn.fujitsu.com>, Mel Gorman <mgorman@suse.de>, Minchan Kim <minchan@kernel.org>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Michal Hocko <mhocko@suse.cz>, James Bottomley <James.Bottomley@HansenPartnership.com>, Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>, David Howells <dhowells@redhat.com>, Mark Salter <msalter@redhat.com>, Jianguo Wu <wujianguo@huawei.com>, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Michel Lespinasse <walken@google.com>

On 04/08/2013 09:39 PM, Rik van Riel wrote:
> On 04/06/2013 09:55 AM, Jiang Liu wrote:
> 
>> @@ -5186,6 +5189,22 @@ early_param("movablecore", cmdline_parse_movablecore);
>>
>>   #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>>
>> +void adjust_managed_page_count(struct page *page, long count)
>> +{
>> +    bool lock = (system_state != SYSTEM_BOOTING);
>> +
>> +    /* No need to acquire the lock during boot */
>> +    if (lock)
>> +        spin_lock(&managed_page_count_lock);
>> +
>> +    page_zone(page)->managed_pages += count;
>> +    totalram_pages += count;
>> +
>> +    if (lock)
>> +        spin_unlock(&managed_page_count_lock);
>> +}
> 
> While I agree the boot code currently does not need the lock, is
> there any harm to removing that conditional?
> 
> That would simplify the code, and protect against possible future
> cleverness of initializing multiple memory things simultaneously.
> 
Hi Rik,
	Thanks for you comments.
	I'm OK with that. Acquiring/releasing the lock should be lightweight
because there shouldn't be contention during boot. Will remove the logic in
next version.
	Regards!
	Gerry

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