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

From: liuchangsheng
Date: Wed Nov 04 2015 - 03:23:54 EST

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",
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@xxxxxxxxxx>
Signed-off-by: Xiaofeng Yan <yanxiaofeng@xxxxxxxxxx>
Tested-by: Dongdong Fan <fandd@xxxxxxxxxx>
Reviewed-by: <yasu.isimatu@xxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
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;

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