[v1 0/6] mm/memblock: Skip prep and initialization of struct pages freed later by HVO

[Usama Arif <usama.arif@bytedance.com>]

If the region is for gigantic hugepages and if HVO is enabled, then those
struct pages which will be freed later by HVO don't need to be prepared and
initialized. This can save significant time when a large number of hugepages
are allocated at boot time.

For a 1G hugepage, this series avoid initialization and preparation of
262144 - 64 = 262080 struct pages per hugepage.

When tested on a 512G system (which can allocate max 500 1G hugepages), the
kexec-boot time with HVO and DEFERRED_STRUCT_PAGE_INIT enabled without this
patchseries to running init is 3.9 seconds. With this patch it is 1.2 seconds.
This represents an approximately 70% reduction in boot time and will
significantly reduce server downtime when using a large number of
gigantic pages.

Thanks,
Usama

[RFC->v1]:
- (Mike Rapoport) Change from passing hugepage_size in
memblock_alloc_try_nid_raw for skipping struct page initialization to
using MEMBLOCK_RSRV_NOINIT flag

Usama Arif (6):
  mm: hugetlb: Skip prep of tail pages when HVO is enabled
  mm: hugetlb_vmemmap: Use nid of the head page to reallocate it
  memblock: add parameter to memblock_setclr_flag for selecting
    memblock_type
  memblock: introduce MEMBLOCK_RSRV_NOINIT flag
  mm: move allocation of gigantic hstates to the start of mm_core_init
  mm: hugetlb: Skip initialization of struct pages freed later by HVO

 include/linux/hugetlb.h  |  1 +
 include/linux/memblock.h |  7 ++++
 mm/hugetlb.c             | 71 ++++++++++++++++++++++++++++++----------
 mm/hugetlb_vmemmap.c     |  6 ++--
 mm/hugetlb_vmemmap.h     | 10 ++++++
 mm/memblock.c            | 51 +++++++++++++++++++++--------
 mm/mm_init.c             |  4 +++
 7 files changed, 117 insertions(+), 33 deletions(-)

-- 
2.25.1