This series moves the boot time initialization of tail struct pages of a
gigantic page to later on in the boot. Only the
HUGETLB_VMEMMAP_RESERVE_SIZE / sizeof(struct page) - 1 tail struct pages
are initialized at the start. If HVO is successful, then no more tail struct
pages need to be initialized. For a 1G hugepage, this series avoid
initialization of 262144 - 63 = 262081 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
[v3->v4]:
- rebase ontop of patch "hugetlb: set hugetlb page flag before optimizing vmemmap".
- freeze head struct page ref count.
- Change order of operations to initialize head struct page -> initialize
the necessary tail struct pages -> attempt HVO -> initialize the rest of the
tail struct pages if HVO fails.
- (Mike Rapoport and Muchun Song) remove "_vmemmap" suffix from memblock reserve
noinit flags anf functions.
[v2->v3]:
- (Muchun Song) skip prep of struct pages backing gigantic hugepages
at boot time only.
- (Muchun Song) move initialization of tail struct pages to after
HVO is attempted.
[v1->v2]:
- (Mike Rapoport) Code quality improvements (function names, arguments,
comments).
[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 (4):
mm: hugetlb_vmemmap: Use nid of the head page to reallocate it
memblock: pass memblock_type to memblock_setclr_flag
memblock: introduce MEMBLOCK_RSRV_NOINIT flag
mm: hugetlb: Skip initialization of gigantic tail struct pages if
freed by HVO
include/linux/memblock.h | 9 ++++++
mm/hugetlb.c | 61 ++++++++++++++++++++++++++++++++++------
mm/hugetlb_vmemmap.c | 4 +--
mm/hugetlb_vmemmap.h | 9 +++---
mm/internal.h | 3 ++
mm/memblock.c | 48 ++++++++++++++++++++++---------
mm/mm_init.c | 2 +-
7 files changed, 107 insertions(+), 29 deletions(-)
--
2.25.1
