When sparse memory model is used an array of memory sections is created to
track each block of contiguous physical pages. Each element of this array
contains PAGES_PER_SECTION pages. During the creation of this array the actual
boundaries of the memory block is lost, so the whole block is either considered
as present or not.
pfn_valid() in the sparse memory configuration checks which memory sections the
pfn belongs to then checks whether it's present or not. This yields sub-optimal
results when the available memory doesn't cover the whole memory section,
because pfn_valid will return 'true' even for the unavailable pfns at the
boundaries of the memory section.
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Yaowei Bai <baiyaowei@xxxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Anthony Liguori <aliguori@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
Signed-off-by: Jan H. Schönherr <jschoenh@xxxxxxxxx>
---
include/linux/mmzone.h | 22 ++++++++++++++++------
mm/sparse.c | 37 ++++++++++++++++++++++++++++++++++++-
2 files changed, 52 insertions(+), 7 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 02069c2..f76a0e1 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1067,8 +1067,12 @@ struct mem_section {
* section. (see page_ext.h about this.)
*/
struct page_ext *page_ext;
- unsigned long pad;
+ unsigned long pad[3];
#endif
+
+ unsigned long first_pfn;
+ unsigned long last_pfn;
+
/*
* WARNING: mem_section must be a power-of-2 in size for the
* calculation and use of SECTION_ROOT_MASK to make sense.
@@ -1140,23 +1144,29 @@ static inline int valid_section_nr(unsigned long nr)
static inline struct mem_section *__pfn_to_section(unsigned long pfn)
{
+ if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
+ return NULL;
+
return __nr_to_section(pfn_to_section_nr(pfn));
}
#ifndef CONFIG_HAVE_ARCH_PFN_VALID
static inline int pfn_valid(unsigned long pfn)
{
- if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
+ struct mem_section *ms;
+
+ ms = __pfn_to_section(pfn);
+
+ if (ms && !(ms->first_pfn <= pfn && ms->last_pfn >= pfn))
return 0;
- return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
+
+ return valid_section(ms);
}
#endif
static inline int pfn_present(unsigned long pfn)
{
- if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
- return 0;
- return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
+ return present_section(__pfn_to_section(pfn));
}
/*
diff --git a/mm/sparse.c b/mm/sparse.c
index 5d0cf45..3c91837 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -166,24 +166,59 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
}
}
+static int __init
+overlaps(u64 start1, u64 end1, u64 start2, u64 end2)
+{
+ u64 start, end;
+
+ start = max(start1, start2);
+ end = min(end1, end2);
+ return start <= end;
+}
+
/* Record a memory area against a node. */
void __init memory_present(int nid, unsigned long start, unsigned long end)
{
+ unsigned long first_pfn = start;
unsigned long pfn;
start &= PAGE_SECTION_MASK;
mminit_validate_memmodel_limits(&start, &end);
for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
unsigned long section = pfn_to_section_nr(pfn);
+ unsigned long last_pfn = min(pfn + PAGES_PER_SECTION, end) - 1;
struct mem_section *ms;
sparse_index_init(section, nid);
set_section_nid(section, nid);
ms = __nr_to_section(section);
- if (!ms->section_mem_map)
+ if (!ms->section_mem_map) {
ms->section_mem_map = sparse_encode_early_nid(nid) |
SECTION_MARKED_PRESENT;
+ } else {
+ /* Merge the two regions */
+ WARN_ON(sparse_early_nid(ms) != nid);
+
+ /*
+ * If they don't overlap there will be a hole in
+ * between where meta-data says it's valid even though
+ * it's not.
+ */
+ if (!overlaps(first_pfn, last_pfn + 1,
+ ms->first_pfn, ms->last_pfn + 1)) {
+ pr_info("Merging non-contiguous pfn ranges 0x%lx-0x%lx and 0x%lx-0x%lx\n",
+ ms->first_pfn, ms->last_pfn,
+ first_pfn, last_pfn);
+ }
+ first_pfn = min(first_pfn, ms->first_pfn);
+ last_pfn = max(last_pfn, ms->last_pfn);
+ }
+
+ ms->first_pfn = first_pfn;
+ ms->last_pfn = last_pfn;
+
+ first_pfn = pfn + PAGES_PER_SECTION;
}
}
--
2.8.2
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