The patch titled
Subject: mm/page_alloc: skip non present sections on zone initialization
has been added to the -mm tree. Its filename is
mm-page_alloc-skip-non-present-sections-on-zone-initialization.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-skip-non-present-sections-on-zone-initialization.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-skip-non-present-sections-on-zone-initialization.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Subject: mm/page_alloc: skip non present sections on zone initialization
memmap_init_zone() can be called on the ranges with holes during the boot.
It will skip any non-valid PFNs one-by-one. It works fine as long as
holes are not too big.
But huge holes in the memory map causes a problem. It takes over 20
seconds to walk 32TiB hole. x86-64 with 5-level paging allows for much
larger holes in the memory map which would practically hang the system.
Deferred struct page init doesn't help here. It only works on the present
ranges.
Skipping non-present sections would fix the issue.
Link: http://lkml.kernel.org/r/20191230093828.24613-1-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: "Jin, Zhi" <zhi.jin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
--- a/mm/page_alloc.c~mm-page_alloc-skip-non-present-sections-on-zone-initialization
+++ a/mm/page_alloc.c
@@ -5847,6 +5847,30 @@ overlap_memmap_init(unsigned long zone,
return false;
}
+#ifdef CONFIG_SPARSEMEM
+/* Skip PFNs that belong to non-present sections */
+static inline __meminit unsigned long next_pfn(unsigned long pfn)
+{
+ unsigned long section_nr;
+
+ section_nr = pfn_to_section_nr(++pfn);
+ if (present_section_nr(section_nr))
+ return pfn;
+
+ while (++section_nr <= __highest_present_section_nr) {
+ if (present_section_nr(section_nr))
+ return section_nr_to_pfn(section_nr);
+ }
+
+ return -1;
+}
+#else
+static inline __meminit unsigned long next_pfn(unsigned long pfn)
+{
+ return pfn++;
+}
+#endif
+
/*
* Initially all pages are reserved - free ones are freed
* up by memblock_free_all() once the early boot process is
@@ -5886,8 +5910,10 @@ void __meminit memmap_init_zone(unsigned
* function. They do not exist on hotplugged memory.
*/
if (context == MEMMAP_EARLY) {
- if (!early_pfn_valid(pfn))
+ if (!early_pfn_valid(pfn)) {
+ pfn = next_pfn(pfn) - 1;
continue;
+ }
if (!early_pfn_in_nid(pfn, nid))
continue;
if (overlap_memmap_init(zone, &pfn))
_
Patches currently in -mm which might be from kirill@xxxxxxxxxxxxx are
thp-fix-conflict-of-above-47bit-hint-address-and-pmd-alignment.patch
thp-shmem-fix-conflict-of-above-47bit-hint-address-and-pmd-alignment.patch
thp-shmem-fix-conflict-of-above-47bit-hint-address-and-pmd-alignment-fix.patch
mm-page_alloc-skip-non-present-sections-on-zone-initialization.patch
