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

[Changsheng Liu <liuchangsheng@inspur.com>]

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.
a?? 2015/8/25 3:15, Yasuaki Ishimatsu a??e??:
> Hi
> On Thu, 20 Aug 2015 14:15:13 +0800
> Changsheng Liu <liuchangsheng@inspur.com> wrote:
>
>> Hi Andrew Morton:
>> First, thanks very much for your review, I will update codes according
>> to  your suggestio
>>
>> a?? 2015/8/20 7:50, Andrew Morton a??e??:
>>> On Wed, 19 Aug 2015 04:18:26 -0400 Changsheng Liu <liuchangsheng@inspur.com> wrote:
>>>
>>>> From: Changsheng Liu <liuchangcheng@inspur.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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