Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Changsheng Liu <liuchangsheng@inspur.com>]

a?? 2015/10/15 0:18, Vlastimil Babka a??e??:
> On 10/12/2015 08:58 AM, Changsheng Liu wrote:
>> From: Changsheng Liu <liuchangcheng@inspur.com>
>>
>> After the user config CONFIG_MOVABLE_NODE,
>> When the memory is hot added, should_add_memory_movable() return 0
>> because all zones including ZONE_MOVABLE are empty,
>> so the memory that was hot added will be assigned to ZONE_NORMAL
>> and ZONE_NORMAL will be created firstly.
>> But we want the whole node to be added to ZONE_MOVABLE by default.
>>
>> So we change should_add_memory_movable(): if the user config
>> CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
>> and the ZONE_NORMAL is empty or the pfn of the hot-added memory
>> is after the end of the ZONE_NORMAL it will always return 1
>> and then the whole node will be added to ZONE_MOVABLE by default.
>> If we want the node to be assigned to ZONE_NORMAL,
>> we can do it as follows:
>> "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
>>
>> By the patch, the behavious of kernel is changed by sysctl,
>> user can automatically create movable memory
>> by only the following udev rule:
>> SUBSYSTEM=="memory", ACTION=="add",
>> ATTR{state}=="offline", ATTR{state}="online"
     I'm sorry for replying you so late due to the busy business trip.
> So just to be clear, we are adding a new sysctl, because the existing
> movable_node kernel option, which is checked by movable_node_is_enabled(), and
> does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
> memory, as that would be a potentially surprising behavior change? Correct? Then
> this should be mentioned in the changelog too, and wherever "movable_node" is
> documented should also mention the new sysctl. Personally, I would expect
> movable_node to affect hot-added memory as well, and would be surprised that it
> doesn't...
     I think it can let the user decides when to use this feature.
     The user can enable the feature when making the hot_added memory  
of a node movable and
     make the feature disable to assign the hot_added memory of the next 
node to ZONE_NORMAL .
>
>> Signed-off-by: Changsheng Liu <liuchangsheng@inspur.com>
>> Signed-off-by: Xiaofeng Yan <yanxiaofeng@inspur.com>
>> Tested-by: Dongdong Fan <fandd@inspur.com>
>> Cc: Wang Nan <wangnan0@huawei.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: Yinghai Lu <yinghai@kernel.org>
>> Cc: Tang Chen <tangchen@cn.fujitsu.com>
>> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>> Cc: Toshi Kani <toshi.kani@hp.com>
>> Cc: Xishi Qiu <qiuxishi@huawei.com>
>> ---
>>   Documentation/memory-hotplug.txt |    5 ++++-
>>   kernel/sysctl.c                  |   15 +++++++++++++++
>>   mm/memory_hotplug.c              |   24 ++++++++++++++++++++++++
>>   3 files changed, 43 insertions(+), 1 deletions(-)
>>
>> diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
>> index ce2cfcf..7ac7485 100644
>> --- a/Documentation/memory-hotplug.txt
>> +++ b/Documentation/memory-hotplug.txt
>> @@ -277,7 +277,7 @@ And if the memory block is in ZONE_MOVABLE, you can change it to ZONE_NORMAL:
>>   After this, memory block XXX's state will be 'online' and the amount of
>>   available memory will be increased.
>>   
>> -Currently, newly added memory is added as ZONE_NORMAL (for powerpc, ZONE_DMA).
>> +Currently, newly added memory is added as ZONE_NORMAL or ZONE_MOVABLE (for powerpc, ZONE_DMA).
>>   This may be changed in future.
>>   
>>   
>> @@ -319,6 +319,9 @@ creates ZONE_MOVABLE as following.
>>     Size of memory not for movable pages (not for offline) is TOTAL - ZZZZ.
>>     Size of memory for movable pages (for offline) is ZZZZ.
>>   
>> +And a sysctl parameter for assigning the hot added memory to ZONE_MOVABLE is
>> +supported. If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
>> +memory will be assigned to ZONE_MOVABLE by default.
>>   
>>   Note: Unfortunately, there is no information to show which memory block belongs
>>   to ZONE_MOVABLE. This is TBD.
>> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
>> index 19b62b5..16b1501 100644
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -166,6 +166,10 @@ extern int unaligned_dump_stack;
>>   extern int no_unaligned_warning;
>>   #endif
>>   
>> +#ifdef CONFIG_MOVABLE_NODE
>> +extern int hotadd_memory_as_movable;
>> +#endif
>> +
>>   #ifdef CONFIG_PROC_SYSCTL
>>   
>>   #define SYSCTL_WRITES_LEGACY	-1
>> @@ -1139,6 +1143,17 @@ static struct ctl_table kern_table[] = {
>>   		.proc_handler	= timer_migration_handler,
>>   	},
>>   #endif
>> +/*If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
>> + * memory will be assigned to ZONE_MOVABLE by default.*/
>> +#ifdef CONFIG_MOVABLE_NODE
>> +	{
>> +		.procname	= "hotadd_memory_as_movable",
>> +		.data		= &hotadd_memory_as_movable,
>> +		.maxlen		= sizeof(int),
>> +		.mode		= 0644,
>> +		.proc_handler	= proc_dointvec,
>> +	},
>> +#endif
>>   	{ }
>>   };
>>   
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 26fbba7..eca5512 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -37,6 +37,11 @@
>>   
>>   #include "internal.h"
>>   
>> +/*If the global variable value is 1,
>> + * the hot added memory will be assigned to ZONE_MOVABLE by default
>> + */
>> +int hotadd_memory_as_movable;
>> +
>>   /*
>>    * online_page_callback contains pointer to current page onlining function.
>>    * Initially it is generic_online_page(). If it is required it could be
>> @@ -1190,6 +1195,9 @@ static int check_hotplug_memory_range(u64 start, u64 size)
>>   /*
>>    * If movable zone has already been setup, newly added memory should be check.
>>    * If its address is higher than movable zone, it should be added as movable.
>> + * And if system config CONFIG_MOVABLE_NODE and set the sysctl parameter
>> + * "hotadd_memory_as_movable" and added memory does not overlap the zone
>> + * before MOVABLE_ZONE,the memory will be added as movable.
>>    * Without this check, movable zone may overlap with other zone.
>>    */
>>   static int should_add_memory_movable(int nid, u64 start, u64 size)
>> @@ -1197,6 +1205,22 @@ static int should_add_memory_movable(int nid, u64 start, u64 size)
>>   	unsigned long start_pfn = start >> PAGE_SHIFT;
>>   	pg_data_t *pgdat = NODE_DATA(nid);
>>   	struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
>> +	struct zone *pre_zone = pgdat->node_zones + (ZONE_MOVABLE - 1);
>> +	/*
>> +	 * The system configs CONFIG_MOVABLE_NODE to assign a node
>> +	 * which has only movable memory,so the hot-added memory should
>> +	 * be assigned to ZONE_MOVABLE by default,
>> +	 * but the function zone_for_memory() assign the hot-added memory
>> +	 * to ZONE_NORMAL(x86_64) by default.Kernel does not allow to
>> +	 * create ZONE_MOVABLE before ZONE_NORMAL,So if the value of
>> +	 * sysctl parameter "hotadd_memory_as_movable" is 1
>> +	 * and the ZONE_NORMAL is empty or the pfn of the hot-added memory
>> +	 * is after the end of ZONE_NORMAL
>> +	 * the hot-added memory will be assigned to ZONE_MOVABLE.
>> +	 */
>> +	if (hotadd_memory_as_movable
>> +	&& (zone_is_empty(pre_zone) || zone_end_pfn(pre_zone) <= start_pfn))
>> +		return 1;
>>   
>>   	if (zone_is_empty(movable_zone))
>>   		return 0;
>>
> .
>

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