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Subject[PATCH v2 2/5] mm: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn()
Date
Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
where possible") optimized the loop in memmap_init_zone(). But there is
still some room for improvement. E.g. if pfn and pfn+1 are in the same
memblock region, we can simply pfn++ instead of doing the binary search
in memblock_next_valid_pfn.

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
include/linux/memblock.h | 2 +-
mm/memblock.c | 73 +++++++++++++++++++++++++++++-------------------
mm/page_alloc.c | 3 +-
3 files changed, 47 insertions(+), 31 deletions(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index efbbe4b..a8fb2ab 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -204,7 +204,7 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

#ifdef CONFIG_HAVE_ARCH_PFN_VALID
-unsigned long memblock_next_valid_pfn(unsigned long pfn);
+unsigned long memblock_next_valid_pfn(unsigned long pfn, int *idx);
#endif

/**
diff --git a/mm/memblock.c b/mm/memblock.c
index bea5a9c..06c1a08 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1102,35 +1102,6 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
*out_nid = r->nid;
}

-#ifdef CONFIG_HAVE_ARCH_PFN_VALID
-unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
-{
- struct memblock_type *type = &memblock.memory;
- unsigned int right = type->cnt;
- unsigned int mid, left = 0;
- phys_addr_t addr = PFN_PHYS(++pfn);
-
- do {
- mid = (right + left) / 2;
-
- if (addr < type->regions[mid].base)
- right = mid;
- else if (addr >= (type->regions[mid].base +
- type->regions[mid].size))
- left = mid + 1;
- else {
- /* addr is within the region, so pfn is valid */
- return pfn;
- }
- } while (left < right);
-
- if (right == type->cnt)
- return -1UL;
- else
- return PHYS_PFN(type->regions[right].base);
-}
-#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
-
/**
* memblock_set_node - set node ID on memblock regions
* @base: base of area to set node ID for
@@ -1162,6 +1133,50 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
}
#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

+#ifdef CONFIG_HAVE_ARCH_PFN_VALID
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
+ int *last_idx)
+{
+ struct memblock_type *type = &memblock.memory;
+ unsigned int right = type->cnt;
+ unsigned int mid, left = 0;
+ unsigned long start_pfn, end_pfn;
+ phys_addr_t addr = PFN_PHYS(++pfn);
+
+ /* fast path, return pfh+1 if next pfn is in the same region */
+ if (*last_idx != -1) {
+ start_pfn = PFN_DOWN(type->regions[*last_idx].base);
+ end_pfn = PFN_DOWN(type->regions[*last_idx].base +
+ type->regions[*last_idx].size);
+
+ if (pfn < end_pfn && pfn > start_pfn)
+ return pfn;
+ }
+
+ /* slow path, do the binary searching */
+ do {
+ mid = (right + left) / 2;
+
+ if (addr < type->regions[mid].base)
+ right = mid;
+ else if (addr >= (type->regions[mid].base +
+ type->regions[mid].size))
+ left = mid + 1;
+ else {
+ *last_idx = mid;
+ return pfn;
+ }
+ } while (left < right);
+
+ if (right == type->cnt)
+ return -1UL;
+
+ *last_idx = right;
+
+ return PHYS_PFN(type->regions[*last_idx].base);
+}
+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
+
static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
phys_addr_t align, phys_addr_t start,
phys_addr_t end, int nid, ulong flags)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2a967f7..0bb0274 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5459,6 +5459,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
unsigned long end_pfn = start_pfn + size;
pg_data_t *pgdat = NODE_DATA(nid);
unsigned long pfn;
+ int idx = -1;
unsigned long nr_initialised = 0;
struct page *page;
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
@@ -5490,7 +5491,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
* end_pfn), such that we hit a valid pfn (or end_pfn)
* on our next iteration of the loop.
*/
- pfn = memblock_next_valid_pfn(pfn) - 1;
+ pfn = memblock_next_valid_pfn(pfn, &idx) - 1;
#endif
continue;
}
--
2.7.4
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