[PATCH 0/3] powerpc/pseries: Manage single copy of ibm, dynamic-memory

Nathan Fontenot nfont at linux.vnet.ibm.com
Sat Aug 27 07:03:51 AEST 2016

The ibm,dynamic-reconfiguration-memory/ibm,dynamic-memory property
of the device-tree can be fairly big on systems with a large amount
of memory. A system with 1 TB of memory (256 MB LMBs) the property
size is 94k, this equates to roughly a 30MB property size for a 32 TB
system. This file size is not neccessarily huge, but the need to update
this property every time we DLPAR add or remove an LMB could be

Every time the property is updated a new copy of the property is made
with the previous copy being added to the old_properties list. Due to
the lack of reference counting on properties old versions of a property
are never free'ed. One a large 32TB system we could easilty do
several thousands of memory add/remove operations and thus create
several thousand of copies of this property. This seems a bit wasteful
with respect to system resources.
Patch 1/3:
This patch changes the pseries hotplug memory code to maintain a static
reference to this property instead of creating a new copy for every LMB
that we add or remove. In doing this we have to ensure that the property
remains in BE format so a set of accessor methods are provided to
get/set values from the property in the proper cpu format.

Patch 2/3:
Remove a no longer need rtas_hp_event flag.

Patch 3/3:
Add a bit field to track updated LMBs during DLPAR add/remove operations.
This should provide an improvement in kernel resources as
we will no longer have un-referenced copies of this property.


Nathan Fontenot (3):
      powerpc/pseries: maintain single copy of ibm,dynamic-memory property
      powerpc/pseries: Remove no longer needed rtas_hp_event flag
      powerpc/pseries: Add bitmap to track updated LMBs

 arch/powerpc/platforms/pseries/hotplug-memory.c |  526 ++++++++++-------------
 1 file changed, 224 insertions(+), 302 deletions(-)

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