linux-kernel - Re: [PATCH V8] mm: memory hot-add: hot-added memory can not be added to movable zone by default

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Date:	Wed, 04 Nov 2015 08:18:11 -0800 (PST)
From:	Yasuaki Ishimatsu <yasu.isimatu@...il.com>
To:	liuchangsheng <liuchangsheng@...pur.com>
Cc:	<akpm@...ux-foundation.org>, <isimatu.yasuaki@...fujitsu.com>,
	<vbabka@...e.cz>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <wunan@...pur.com>,
	<yanxiaofeng@...pur.com>, <fandd@...pur.com>,
	Wang Nan <wangnan0@...wei.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>, Xishi Qiu <qiuxishi@...wei.com>
Subject: Re: [PATCH V8] mm: memory hot-add: hot-added memory can not be
 added to movable zone by default


On Wed, 4 Nov 2015 03:23:35 -0500
liuchangsheng <liuchangsheng@...pur.com> wrote:

> 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 we need using the udev rules to online the memory automatically:
> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline",
> ATTR{state}="online_movable"
> The memory block onlined by udev must be adjacent to ZONE_MOVABLE.
> The events of memory section are notified to udev asynchronously,
> so it can not ensure that the memory block onlined by udev is
> adjacent to ZONE_MOVABLE.So it can't ensure memory online always success.
> 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 movable_node kernel option
> 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"
> 
> Signed-off-by: liuchangsheng <liuchangsheng@...pur.com>
> Signed-off-by: Xiaofeng Yan <yanxiaofeng@...pur.com>
> Tested-by: Dongdong Fan <fandd@...pur.com>
> Reviewed-by: <yasu.isimatu@...il.com>
> Cc: Wang Nan <wangnan0@...wei.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Yinghai Lu <yinghai@...nel.org>
> Cc: Tang Chen <tangchen@...fujitsu.com>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: Toshi Kani <toshi.kani@...com>
> Cc: Xishi Qiu <qiuxishi@...wei.com>
> ---

Looks good to me.

Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>

Thanks,
Yasuaki Ishimatsu

>  mm/memory_hotplug.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index aa992e2..8617b9f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1201,6 +1201,9 @@ 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)
> @@ -1208,6 +1211,10 @@ 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 (zone_is_empty(movable_zone))
>  		return 0;
> -- 
> 1.8.3.1
> 
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