From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: mm/sparsemem: add helpers track active portions of a section at boot
Prepare for hot{plug,remove} of sub-ranges of a section by tracking a
sub-section active bitmask, each bit representing a PMD_SIZE span of the
architecture's memory hotplug section size.
The implications of a partially populated section is that pfn_valid()
needs to go beyond a valid_section() check and either determine that the
section is an "early section", or read the sub-section active ranges from
the bitmask. The expectation is that the bitmask (subsection_map) fits in
the same cacheline as the valid_section() / early_section() data, so the
incremental performance overhead to pfn_valid() should be negligible.
The rationale for using early_section() to short-ciruit the subsection_map
check is that there are legacy code paths that use pfn_valid() at section
granularity before validating the pfn against pgdat data. So, the
early_section() check allows those traditional assumptions to persist
while also permitting subsection_map to tell the truth for purposes of
populating the unused portions of early sections with PMEM and other
ZONE_DEVICE mappings.
Link: http://lkml.kernel.org/r/156092350874.979959.18185938451405518285.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reported-by: Qian Cai <cai@xxxxxx>
Tested-by: Jane Chu <jane.chu@xxxxxxxxxx>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> [ppc64]
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 33 ++++++++++++++++++++++++++++++++-
mm/page_alloc.c | 10 ++++++++--
mm/sparse.c | 35 +++++++++++++++++++++++++++++++++++
3 files changed, 75 insertions(+), 3 deletions(-)
--- a/include/linux/mmzone.h~mm-sparsemem-add-helpers-track-active-portions-of-a-section-at-boot
+++ a/include/linux/mmzone.h
@@ -1178,6 +1178,8 @@ struct mem_section_usage {
unsigned long pageblock_flags[0];
};
+void subsection_map_init(unsigned long pfn, unsigned long nr_pages);
+
struct page;
struct page_ext;
struct mem_section {
@@ -1321,12 +1323,40 @@ static inline struct mem_section *__pfn_
extern unsigned long __highest_present_section_nr;
+static inline int subsection_map_index(unsigned long pfn)
+{
+ return (pfn & ~(PAGE_SECTION_MASK)) / PAGES_PER_SUBSECTION;
+}
+
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
+{
+ int idx = subsection_map_index(pfn);
+
+ return test_bit(idx, ms->usage->subsection_map);
+}
+#else
+static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
+{
+ return 1;
+}
+#endif
+
#ifndef CONFIG_HAVE_ARCH_PFN_VALID
static inline int pfn_valid(unsigned long pfn)
{
+ struct mem_section *ms;
+
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;
- return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
+ ms = __nr_to_section(pfn_to_section_nr(pfn));
+ if (!valid_section(ms))
+ return 0;
+ /*
+ * Traditionally early sections always returned pfn_valid() for
+ * the entire section-sized span.
+ */
+ return early_section(ms) || pfn_section_valid(ms, pfn);
}
#endif
@@ -1358,6 +1388,7 @@ void sparse_init(void);
#define sparse_init() do {} while (0)
#define sparse_index_init(_sec, _nid) do {} while (0)
#define pfn_present pfn_valid
+#define subsection_map_init(_pfn, _nr_pages) do {} while (0)
#endif /* CONFIG_SPARSEMEM */
/*
--- a/mm/page_alloc.c~mm-sparsemem-add-helpers-track-active-portions-of-a-section-at-boot
+++ a/mm/page_alloc.c
@@ -7351,12 +7351,18 @@ void __init free_area_init_nodes(unsigne
(u64)zone_movable_pfn[i] << PAGE_SHIFT);
}
- /* Print out the early node map */
+ /*
+ * Print out the early node map, and initialize the
+ * subsection-map relative to active online memory ranges to
+ * enable future "sub-section" extensions of the memory map.
+ */
pr_info("Early memory node ranges\n");
- for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
+ for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
pr_info(" node %3d: [mem %#018Lx-%#018Lx]\n", nid,
(u64)start_pfn << PAGE_SHIFT,
((u64)end_pfn << PAGE_SHIFT) - 1);
+ subsection_map_init(start_pfn, end_pfn - start_pfn);
+ }
/* Initialise every node */
mminit_verify_pageflags_layout();
--- a/mm/sparse.c~mm-sparsemem-add-helpers-track-active-portions-of-a-section-at-boot
+++ a/mm/sparse.c
@@ -210,6 +210,41 @@ static inline unsigned long first_presen
return next_present_section_nr(-1);
}
+void subsection_mask_set(unsigned long *map, unsigned long pfn,
+ unsigned long nr_pages)
+{
+ int idx = subsection_map_index(pfn);
+ int end = subsection_map_index(pfn + nr_pages - 1);
+
+ bitmap_set(map, idx, end - idx + 1);
+}
+
+void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
+{
+ int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
+ int i, start_sec = pfn_to_section_nr(pfn);
+
+ if (!nr_pages)
+ return;
+
+ for (i = start_sec; i <= end_sec; i++) {
+ struct mem_section *ms;
+ unsigned long pfns;
+
+ pfns = min(nr_pages, PAGES_PER_SECTION
+ - (pfn & ~PAGE_SECTION_MASK));
+ ms = __nr_to_section(i);
+ subsection_mask_set(ms->usage->subsection_map, pfn, pfns);
+
+ pr_debug("%s: sec: %d pfns: %ld set(%d, %d)\n", __func__, i,
+ pfns, subsection_map_index(pfn),
+ subsection_map_index(pfn + pfns - 1));
+
+ pfn += pfns;
+ nr_pages -= pfns;
+ }
+}
+
/* Record a memory area against a node. */
void __init memory_present(int nid, unsigned long start, unsigned long end)
{
_
