RFC mm: Deferred page init improvements

This patchset is essentially a refactor of the page initialization logic to provide for better code reuse while providing a significant improvement in deferred page initialization performance.

In my testing I have seen a 3:1 reduction in the time needed for deferred memory initialization on two different x86_64 based test systems I have.

In addition this provides a very slight improvement for the hotplug memory initialization, although the improvement doesn't exceed 5% from what I can tell and that is to be expected since most of the changes related to hotplug initialization are just code clean-up to allow for reuse. I had been considering using a large memset for the entire pageblock I was initializing which showed a significant speedup for persistent memory init however that showed no improvements to a slight regression for regular deferred initialization of standard memory.

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Alexander Duyck (5):
mm: Use mm_zero_struct_page from SPARC on all 64b architectures
mm: Drop meminit_pfn_in_nid as it is redundant
mm: Use memblock/zone specific iterator for handling deferred page init
mm: Move hot-plug specific memory init into separate functions and optimize
mm: Use common iterator for deferred_init_pages and deferred_free_pages

 arch/sparc/include/asm/pgtable_64.h |   30 --
 include/linux/memblock.h            |   58 ++++
 include/linux/mm.h                  |   33 ++
 mm/memblock.c                       |   63 ++++
 mm/page_alloc.c                     |  555 +++++++++++++++++++++--------------
 5 files changed, 485 insertions(+), 254 deletions(-)

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