linux-kernel - Re: [PATCH] Memory hot added,The memory can not been added to movable zone

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Date:	Tue, 25 Aug 2015 13:13:07 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Changsheng Liu <liuchangsheng@...pur.com>,
	Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	isimatu.yasuaki@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, yanxiaofeng@...pur.com,
	Changsheng Liu <liuchangcheng@...pur.com>
Subject: Re: [PATCH] Memory hot added,The memory can not been added to movable
 zone

On 08/25/2015 12:25 PM, Changsheng Liu wrote:
> Thanks very much for your review, I can move the memory from normal zone
> to movable zone succesfully.
> And thank you for let me understand the memory mechanism better.
> 在 2015/8/25 3:15, Yasuaki Ishimatsu 写道:

So you agree to drop the patch from -mm?

>> Hi
>> On Thu, 20 Aug 2015 14:15:13 +0800
>> Changsheng Liu <liuchangsheng@...pur.com> wrote:
>>
>>> Hi Andrew Morton:
>>> First, thanks very much for your review, I will update codes according
>>> to  your suggestio
>>>
>>> 在 2015/8/20 7:50, Andrew Morton 写道:
>>>> On Wed, 19 Aug 2015 04:18:26 -0400 Changsheng Liu <liuchangsheng@...pur.com> wrote:
>>>>
>>>>> From: Changsheng Liu <liuchangcheng@...pur.com>
>>>>>
>>>>> When memory hot added, the function should_add_memory_movable
>>>>> always return 0,because the movable zone is empty,
>>>>> so the memory that hot added will add to normal zone even if
>>>>> we want to remove the memory.
>>>>> So we change the function should_add_memory_movable,if the user
>>>>> config CONFIG_MOVABLE_NODE it will return 1 when
>>>>> movable zone is empty
>>>> I cleaned this up a bit:
>>>>
>>>> : Subject: mm: memory hot-add: memory can not been added to movable zone
>>>> :
>>>> : When memory is hot added, should_add_memory_movable() always returns 0
>>>> : because the movable zone is empty, so the memory that was hot added will
>>>> : add to the normal zone even if we want to remove the memory.
>>>> :
>>>> : So we change should_add_memory_movable(): if the user config
>>>> : CONFIG_MOVABLE_NODE it will return 1 when the movable zone is empty.
>>>>
>>>> But I don't understand the "even if we want to remove the memory".
>>>> This is hot-add, not hot-remove.  What do you mean here?
>>>        After the system startup, we hot added one memory. After some time
>>> we wanted to hot remove the memroy that was hot added,
>>>        but we could not offline some memory blocks successfully because
>>> the memory was added to normal zone defaultly and the value of the file
>>>        named removable under some memory blocks is 0.
>> For this, we prepared online_movable. When memory is onlined by online_movable,
>> the memory move from ZONE_NORMAL to ZONE_MOVABLE.
>>
>> Ex.
>> # echo online_movable > /sys/devices/system/memory/memoryXXX/state
>>
>> Thanks,
>> Yasuaki Ishimatsu
>>
>>>        we checked the value of the file under some memory blocks as follows:
>>>        "cat /sys/devices/system/memory/ memory***/removable"
>>>        When memory being hot added we let the memory be added to movable
>>> zone,
>>>        so we will be able to hot remove the memory that have been hot added
>>>>> --- a/mm/memory_hotplug.c
>>>>> +++ b/mm/memory_hotplug.c
>>>>> @@ -1198,9 +1198,13 @@ static int should_add_memory_movable(int nid, u64 start, u64 size)
>>>>>     	pg_data_t *pgdat = NODE_DATA(nid);
>>>>>     	struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
>>>>>
>>>>> -	if (zone_is_empty(movable_zone))
>>>>> +	if (zone_is_empty(movable_zone)) {
>>>>> +	#ifdef CONFIG_MOVABLE_NODE
>>>>> +		return 1;
>>>>> +	#else
>>>>>     		return 0;
>>>>> -
>>>>> +	#endif
>>>>> +	}
>>>>>     	if (movable_zone->zone_start_pfn <= start_pfn)
>>>>>     		return 1;
>>>> Cleaner:
>>>>
>>>> --- a/mm/memory_hotplug.c~memory-hot-addedthe-memory-can-not-been-added-to-movable-zone-fix
>>>> +++ a/mm/memory_hotplug.c
>>>> @@ -1181,13 +1181,9 @@ static int should_add_memory_movable(int
>>>>     	pg_data_t *pgdat = NODE_DATA(nid);
>>>>     	struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
>>>>
>>>> -	if (zone_is_empty(movable_zone)) {
>>>> -	#ifdef CONFIG_MOVABLE_NODE
>>>> -		return 1;
>>>> -	#else
>>>> -		return 0;
>>>> -	#endif
>>>> -	}
>>>> +	if (zone_is_empty(movable_zone))
>>>> +		return IS_ENABLED(CONFIG_MOVABLE_NODE);
>>>> +
>>>>     	if (movable_zone->zone_start_pfn <= start_pfn)
>>>>     		return 1;
>>>>
>>>> _
>>>>
>>>> .
>>>>
>> .
>>
>

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