On Tue, Nov 27, 2012 at 4:29 PM, Tang Chen <tangchen@xxxxxxxxxxxxxx> wrote: > On 11/27/2012 04:00 PM, Bob Liu wrote: >> >> Hi Tang, >> >> On Fri, Nov 23, 2012 at 6:44 PM, Tang Chen<tangchen@xxxxxxxxxxxxxx> >> 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. > Thank you for your explanation. It's reasonable. But i think it's a bit duplicated with CMA, i'm not sure but maybe we can combine it with CMA which already in mainline? > 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 "5.2.16.2 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 >>> ZONE_MOVABLE. >>> >>> 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 >>> have ZONE_MOVABLE. >>> 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(-) >>> >>> -- >>> To unsubscribe, send a message with 'unsubscribe linux-mm' in >>> the body to majordomo@xxxxxxxxx. For more info on Linux MM, >>> see: http://www.linux-mm.org/ . >>> Don't email:<a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx</a> >> >> > -- Regards, --Bob -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>