a?? 2015/8/27 17:29, Vlastimil Babka a??e??:

On 08/27/2015 10:54 AM, Changsheng Liu wrote:

quoted

From: Changsheng Liu <redacted>

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.

OK it seems current behavior indeed goes against the expectations of 
setting movable_node.

quoted

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.

Was this tested to really work as well? Per Yasuaki's explanation in 
v2, you shouldn't create ZONE_MOVABLE before ZONE_NORMAL.

     We will test it more fully.
     There is on limit written in Documentation/memory-hotplug.txt when 
move the memory from movable zone to normal zone:
     echo online_kernel > /sys/devices/system/memory/memoryXXX/state
     (NOTE: current limit: this memory block must be adjacent to 
ZONE_NORMAL)

     The zone will be created as follows:
     First,all zones have been initialized,but all zones are empty, then 
the should_add_memory_movable() return 1 so the movable is created and 
add the whole node to movable zone.
             empty                 whole node's memory
     |-------------------|-------------------------------|---
      ZONE_NORMAL     ZONE_MOVABLE

    when we  move the memory to normal zone
empty whole node's memory
|--------------------|----------------------------------------------------:-------------------------------------------|
                                   one memory block ajacent to 
ZONE_NORMAL  :
      ZONE_NORMAL   ZONE_MOVABLE            :
                                       :
                                  one memory block 
                                             :    whole node  - one 
memory block
|-------------------------------------------------------------------------|-------------------------------------------|
      ZONE_NORMAL                           ZONE_MOVABLE

quoted

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>

Interesting...

quoted

Signed-off-by: Changsheng Liu <redacted>i
Tested-by: Dongdong Fan <redacted>
---
  mm/memory_hotplug.c |    3 +++
  1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 26fbba7..b5f14fa 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c

@@ -1198,6 +1198,9 @@ static int should_add_memory_movable(int nid, 

u64 start, u64 size)
      pg_data_t *pgdat = NODE_DATA(nid);
      struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;

+    if (movable_node_is_enabled())
+        return 1;
+
      if (zone_is_empty(movable_zone))
          return 0;

.

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