Re: [PATCH V5] mm: memory hot-add: memory can not be added to movable zone defaultly

[Yasuaki Ishimatsu]

Hi Changsheng,

According to the following thread, Tang has no objection to change kernel
behavior since udev cannot online memory as movable.

https://lkml.org/lkml/2015/10/21/159

So how about reposting the v5 patch?
I have a comment about the patch. Please see below.

On Tue, 15 Sep 2015 03:49:58 -0400
Changsheng Liu <liuchangsheng@xxxxxxxxxx> wrote:

> From: Changsheng Liu <liuchangcheng@xxxxxxxxxx>
> 
> After the user config CONFIG_MOVABLE_NODE and movable_node kernel option,
> When the memory is hot added, should_add_memory_movable() return 0
> because all zones including movable zone are empty,
> so the memory that was hot added will be added  to the normal zone
> and the normal zone will be created firstly.
> But we want the whole node to be added to movable zone defaultly.
> 
> So we change should_add_memory_movable(): if the user config
> CONFIG_MOVABLE_NODE and movable_node kernel option
> it will always return 1 and all zones is empty at the same time,
> so that the movable zone will be created firstly
> and then the whole node will be added to movable zone defaultly.
> If we want the node to be added to normal zone,
> we can do it as follows:
> "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> 
> Signed-off-by: Xiaofeng Yan <yanxiaofeng@xxxxxxxxxx>
> Signed-off-by: Changsheng Liu <liuchangcheng@xxxxxxxxxx>
> Tested-by: Dongdong Fan <fandd@xxxxxxxxxx>
> ---
>  mm/memory_hotplug.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 26fbba7..d39dbb0 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1190,6 +1190,9 @@ 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 boots up with movable_node and config CONFIG_MOVABLE_NOD and
> + * added memory does not overlap the zone before MOVABLE_ZONE,
> + * the memory is 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 +1200,11 @@ 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);
> +

> +	if (movable_node_is_enabled()
> +	&& zone_end_pfn(pre_zone) <= start_pfn)
> +		return 1;

	if (movable_node_is_enabled() && (zone_end_pfn(pre_zone) <= start_pfn))

Thanks,
Yasuaki Ishimatsu

>  
>  	if (zone_is_empty(movable_zone))
>  		return 0;
> -- 
> 1.7.1
> 
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