Re: [PATCH V4] mm: memory hot-add: memory can not be added to movable zone defaultly

[Yasuaki Ishimatsu <yasu.isimatu@gmail.com>]

On Mon, 31 Aug 2015 01:58:40 -0400
Changsheng Liu <liuchangsheng@inspur.com> wrote:

> From: Changsheng Liu <liuchangcheng@inspur.com>
> 
> 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"
> 
> If the memory is added to movable zone defaultly,
> the user can offline it and add it to other zone again.
> But if the memory is added to normal zone defaultly,
> the user will not offline the memory used by kernel.
> 
> Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
> Reviewed-by: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> Reviewed-by: Xiaofeng Yan <yanxiaofeng@inspur.com>
> Signed-off-by: Changsheng Liu <liuchangcheng@inspur.com>
> Tested-by: Dongdong Fan <fandd@inspur.com>
> ---
>  mm/memory_hotplug.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 26fbba7..d1149ff 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1197,6 +1197,11 @@ 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 *normal_zone = pgdat->node_zones + ZONE_NORMAL;
> +
> +	if (movable_node_is_enabled()
> +	&& (zone_end_pfn(normal_zone) <= start_pfn))
> +		return 1;

If system boots up without movable_node, kernel behavior is changed by the patch.
And you syould consider other zone.

How about it. The patch is no build and test.


---
 mm/memory_hotplug.c |   36 ++++++++++++++++++++++++++++++++----
 1 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6da82bc..321595d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1198,6 +1198,8 @@ 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_zone and added memory does not overlap
+ * other zone except for 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)
@@ -1205,14 +1207,40 @@ 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 *zone;
+	enum zone_type zt = ZONE_MOVABLE - 1;
+
+	/*
+	 * If memory is added after ZONE_MOVALBE, the memory is managed as
+	 * movable.
+	 */
+	if (!zone_is_empty(movable_zone) &&
+	    (movable_zone->zone_start_pfn <= start_pfn))
+		return 1;
 
-	if (zone_is_empty(movable_zone))
+	if (!movable_node_is_enabled())
 		return 0;
 
-	if (movable_zone->zone_start_pfn <= start_pfn)
-		return 1;
+	/*
+	 * Find enabled zone and check the added memory.
+	 * If the memory is added after the enabled zone, the memory is
+	 * managed as movable.
+	 *
+	 * If all zones are empty, the memory is also managed as movable.
+	 */
+	for (; zt >= ZONE_DMA; zt--) {
+		zone = pgdat->node_zones + zt;
 
-	return 0;
+		if (zone_is_empty(zone))
+			continue;
+
+		if (zone_end_pfn(zone) <= start_pfn)
+			return 1;
+		else
+			return 0;
+	}
+
+	return 1;
 }
 
 int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
-- 
1.7.1



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