RFC mm: mirrored memory support for page buddy allocations

Intel Xeon processor E7 v3 product family-based platforms introduces support for partial memory mirroring called as 'Address Range Mirroring'. This feature allows BIOS to specify a subset of total available memory to be mirrored (and optionally also specify whether to mirror the range 0-4 GB). This capability allows user to make an appropriate tradeoff between non-mirrored memory range and mirrored memory range thus optimizing total available memory and still achieving highly reliable memory range for mission critical workloads and/or kernel space.

Tony has already send a patchset to supprot this feature at boot time.
https://lkml.org/lkml/2015/5/8/521
This patchset is based on Tony's, it can support the feature after boot time. Use mirrored memory for all kernel allocations.

TBD:
- Add compatibility with memory online/offline, memory compaction, CMA...
- Need to discuss the implementation ideas, add a new zone or a new migratetype or others.

V2:
- Use memblock which marked MEMBLOCK_MIRROR to find mirrored memory instead of mirror_info.
- Remove __GFP_MIRROR and /proc/sys/vm/mirrorable.
- Use mirrored memory for all kernel allocations.

Xishi Qiu (8):
mm: add a new config to manage the code
mm: introduce MIGRATE_MIRROR to manage the mirrored pages
mm: find mirrored memory in memblock
mm: add mirrored memory to buddy system
mm: introduce a new zone_stat_item NR_FREE_MIRROR_PAGES
mm: add free mirrored pages info
mm: add the buddy system interface
mm: add the PCP interface

 drivers/base/node.c      |  17 ++++---
 fs/proc/meminfo.c        |   6 +++
 include/linux/memblock.h |  29 ++++++++++--
 include/linux/mmzone.h   |  10 ++++
 include/linux/vmstat.h   |   2 +
 mm/Kconfig               |   8 ++++
 mm/memblock.c            |  33 +++++++++++--
 mm/nobootmem.c           |   3 ++
 mm/page_alloc.c          | 117 ++++++++++++++++++++++++++++++++++++-----------
 mm/vmstat.c              |   4 ++
 10 files changed, 190 insertions(+), 39 deletions(-)

2.0.0