[v4 00/15] complete deferred page initialization

From: Pavel Tatashin
Date: Wed Aug 02 2017 - 16:39:43 EST

v3 - v2
- Rewrote code to zero sturct pages in __init_single_page() as
suggested by Michal Hocko
- Added code to handle issues related to accessing struct page
memory before they are initialized.

v2 - v3
- Addressed David Miller comments about one change per patch:
* Splited changes to platforms into 4 patches
* Made "do not zero vmemmap_buf" as a separate patch

v1 - v2
- Per request, added s390 to deferred "struct page" zeroing
- Collected performance data on x86 which proofs the importance to
keep memset() as prefetch (see below).

SMP machines can benefit from the DEFERRED_STRUCT_PAGE_INIT config option,
which defers initializing struct pages until all cpus have been started so
it can be done in parallel.

However, this feature is sub-optimal, because the deferred page
initialization code expects that the struct pages have already been zeroed,
and the zeroing is done early in boot with a single thread only. Also, we
access that memory and set flags before struct pages are initialized. All
of this is fixed in this patchset.

In this work we do the following:
- Never read access struct page until it was initialized
- Never set any fields in struct pages before they are initialized
- Zero struct page at the beginning of struct page initialization

Performance improvements on x86 machine with 8 nodes:
Intel(R) Xeon(R) CPU E7-8895 v3 @ 2.60GHz

Single threaded struct page init: 7.6s/T improvement
Deferred struct page init: 10.2s/T improvement

Pavel Tatashin (15):
x86/mm: reserve only exiting low pages
x86/mm: setting fields in deferred pages
sparc64/mm: setting fields in deferred pages
mm: discard memblock data later
mm: don't accessed uninitialized struct pages
sparc64: simplify vmemmap_populate
mm: defining memblock_virt_alloc_try_nid_raw
mm: zero struct pages during initialization
sparc64: optimized struct page zeroing
x86/kasan: explicitly zero kasan shadow memory
arm64/kasan: explicitly zero kasan shadow memory
mm: explicitly zero pagetable memory
mm: stop zeroing memory during allocation in vmemmap
mm: optimize early system hash allocations
mm: debug for raw alloctor

arch/arm64/mm/kasan_init.c | 32 ++++++++
arch/sparc/include/asm/pgtable_64.h | 18 +++++
arch/sparc/mm/init_64.c | 31 +++-----
arch/x86/kernel/setup.c | 5 +-
arch/x86/mm/init_64.c | 9 ++-
arch/x86/mm/kasan_init_64.c | 29 +++++++
include/linux/bootmem.h | 11 +++
include/linux/memblock.h | 10 ++-
include/linux/mm.h | 9 +++
mm/memblock.c | 152 ++++++++++++++++++++++++++++--------
mm/nobootmem.c | 16 ----
mm/page_alloc.c | 29 ++++---
mm/sparse-vmemmap.c | 10 ++-
mm/sparse.c | 6 +-
14 files changed, 279 insertions(+), 88 deletions(-)