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SubjectRe: [PATCH v2 0/5] Add movablecore_map boot option
On 11/27/2012 04:00 PM, Bob Liu wrote:
> Hi Tang,
> On Fri, Nov 23, 2012 at 6:44 PM, Tang Chen<> wrote:
>> [What we are doing]
>> This patchset provide a boot option for user to specify ZONE_MOVABLE memory
>> map for each node in the system.
>> movablecore_map=nn[KMG]@ss[KMG]
>> This option make sure memory range from ss to ss+nn is movable memory.
>> [Why we do this]
>> If we hot remove a memroy, the memory cannot have kernel memory,
>> because Linux cannot migrate kernel memory currently. Therefore,
>> we have to guarantee that the hot removed memory has only movable
>> memoroy.
>> Linux has two boot options, kernelcore= and movablecore=, for
>> creating movable memory. These boot options can specify the amount
>> of memory use as kernel or movable memory. Using them, we can
>> create ZONE_MOVABLE which has only movable memory.
>> But it does not fulfill a requirement of memory hot remove, because
>> even if we specify the boot options, movable memory is distributed
>> in each node evenly. So when we want to hot remove memory which
>> memory range is 0x80000000-0c0000000, we have no way to specify
>> the memory as movable memory.
> Sorry, I'm still not get your idea.
> Why you need a specify range that is movable?
> Could you describe the requirement and situation a bit more?
> Thank you.

Hi Liu,

This feature is used in memory hotplug.

In order to implement a whole node hotplug, we need to make sure the
node contains no kernel memory, because memory used by kernel could
not be migrated. (Since the kernel memory is directly mapped,
VA = PA + __PAGE_OFFSET. So the physical address could not be changed.)

User could specify all the memory on a node to be movable, so that the
node could be hot-removed.

Another approach is like the following:
movable_node = 1,3-5,8
This could set all the memory on the nodes to be movable. And the rest
of memory works as usual. But movablecore_map is more flexible.

Thanks. :)

>> So we proposed a new feature which specifies memory range to use as
>> movable memory.
>> [Ways to do this]
>> There may be 2 ways to specify movable memory.
>> 1. use firmware information
>> 2. use boot option
>> 1. use firmware information
>> According to ACPI spec 5.0, SRAT table has memory affinity structure
>> and the structure has Hot Pluggable Filed. See " Memory
>> Affinity Structure". If we use the information, we might be able to
>> specify movable memory by firmware. For example, if Hot Pluggable
>> Filed is enabled, Linux sets the memory as movable memory.
>> 2. use boot option
>> This is our proposal. New boot option can specify memory range to use
>> as movable memory.
>> [How we do this]
>> We chose second way, because if we use first way, users cannot change
>> memory range to use as movable memory easily. We think if we create
>> movable memory, performance regression may occur by NUMA. In this case,
>> user can turn off the feature easily if we prepare the boot option.
>> And if we prepare the boot optino, the user can select which memory
>> to use as movable memory easily.
>> [How to use]
>> Specify the following boot option:
>> movablecore_map=nn[KMG]@ss[KMG]
>> That means physical address range from ss to ss+nn will be allocated as
>> And the following points should be considered.
>> 1) If the range is involved in a single node, then from ss to the end of
>> the node will be ZONE_MOVABLE.
>> 2) If the range covers two or more nodes, then from ss to the end of
>> the node will be ZONE_MOVABLE, and all the other nodes will only
>> 3) If no range is in the node, then the node will have no ZONE_MOVABLE
>> unless kernelcore or movablecore is specified.
>> 4) This option could be specified at most MAX_NUMNODES times.
>> 5) If kernelcore or movablecore is also specified, movablecore_map will have
>> higher priority to be satisfied.
>> 6) This option has no conflict with memmap option.
>> Tang Chen (4):
>> page_alloc: add movable_memmap kernel parameter
>> page_alloc: Introduce zone_movable_limit[] to keep movable limit for
>> nodes
>> page_alloc: Make movablecore_map has higher priority
>> page_alloc: Bootmem limit with movablecore_map
>> Yasuaki Ishimatsu (1):
>> x86: get pg_data_t's memory from other node
>> Documentation/kernel-parameters.txt | 17 +++
>> arch/x86/mm/numa.c | 11 ++-
>> include/linux/memblock.h | 1 +
>> include/linux/mm.h | 11 ++
>> mm/memblock.c | 15 +++-
>> mm/page_alloc.c | 216 ++++++++++++++++++++++++++++++++++-
>> 6 files changed, 263 insertions(+), 8 deletions(-)
>> --
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