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Subject[PATCH v11 3/3] 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.

Furthermore, if the pfn is in a gap of two memory region, skip to next
region directly if possible.

Attached the memblock region information in my server.
[ 0.000000] Zone ranges:
[ 0.000000] DMA32 [mem 0x0000000000200000-0x00000000ffffffff]
[ 0.000000] Normal [mem 0x0000000100000000-0x00000017ffffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000200000-0x000000000021ffff]
[ 0.000000] node 0: [mem 0x0000000000820000-0x000000000307ffff]
[ 0.000000] node 0: [mem 0x0000000003080000-0x000000000308ffff]
[ 0.000000] node 0: [mem 0x0000000003090000-0x00000000031fffff]
[ 0.000000] node 0: [mem 0x0000000003200000-0x00000000033fffff]
[ 0.000000] node 0: [mem 0x0000000003410000-0x00000000034fffff]
[ 0.000000] node 0: [mem 0x0000000003500000-0x000000000351ffff]
[ 0.000000] node 0: [mem 0x0000000003520000-0x000000000353ffff]
[ 0.000000] node 0: [mem 0x0000000003540000-0x0000000003e3ffff]
[ 0.000000] node 0: [mem 0x0000000003e40000-0x0000000003e7ffff]
[ 0.000000] node 0: [mem 0x0000000003e80000-0x0000000003ecffff]
[ 0.000000] node 0: [mem 0x0000000003ed0000-0x0000000003ed5fff]
[ 0.000000] node 0: [mem 0x0000000003ed6000-0x0000000006eeafff]
[ 0.000000] node 0: [mem 0x0000000006eeb000-0x000000000710ffff]
[ 0.000000] node 0: [mem 0x0000000007110000-0x0000000007f0ffff]
[ 0.000000] node 0: [mem 0x0000000007f10000-0x0000000007faffff]
[ 0.000000] node 0: [mem 0x0000000007fb0000-0x000000000806ffff]
[ 0.000000] node 0: [mem 0x0000000008070000-0x00000000080affff]
[ 0.000000] node 0: [mem 0x00000000080b0000-0x000000000832ffff]
[ 0.000000] node 0: [mem 0x0000000008330000-0x000000000836ffff]
[ 0.000000] node 0: [mem 0x0000000008370000-0x000000000838ffff]
[ 0.000000] node 0: [mem 0x0000000008390000-0x00000000083a9fff]
[ 0.000000] node 0: [mem 0x00000000083aa000-0x00000000083bbfff]
[ 0.000000] node 0: [mem 0x00000000083bc000-0x00000000083fffff]
[ 0.000000] node 0: [mem 0x0000000008400000-0x000000000841ffff]
[ 0.000000] node 0: [mem 0x0000000008420000-0x000000000843ffff]
[ 0.000000] node 0: [mem 0x0000000008440000-0x000000000865ffff]
[ 0.000000] node 0: [mem 0x0000000008660000-0x000000000869ffff]
[ 0.000000] node 0: [mem 0x00000000086a0000-0x00000000086affff]
[ 0.000000] node 0: [mem 0x00000000086b0000-0x00000000086effff]
[ 0.000000] node 0: [mem 0x00000000086f0000-0x0000000008b6ffff]
[ 0.000000] node 0: [mem 0x0000000008b70000-0x0000000008bbffff]
[ 0.000000] node 0: [mem 0x0000000008bc0000-0x0000000008edffff]
[ 0.000000] node 0: [mem 0x0000000008ee0000-0x0000000008ee0fff]
[ 0.000000] node 0: [mem 0x0000000008ee1000-0x0000000008ee2fff]
[ 0.000000] node 0: [mem 0x0000000008ee3000-0x000000000decffff]
[ 0.000000] node 0: [mem 0x000000000ded0000-0x000000000defffff]
[ 0.000000] node 0: [mem 0x000000000df00000-0x000000000fffffff]
[ 0.000000] node 0: [mem 0x0000000010800000-0x0000000017feffff]
[ 0.000000] node 0: [mem 0x000000001c000000-0x000000001c00ffff]
[ 0.000000] node 0: [mem 0x000000001c010000-0x000000001c7fffff]
[ 0.000000] node 0: [mem 0x000000001c810000-0x000000007efbffff]
[ 0.000000] node 0: [mem 0x000000007efc0000-0x000000007efdffff]
[ 0.000000] node 0: [mem 0x000000007efe0000-0x000000007efeffff]
[ 0.000000] node 0: [mem 0x000000007eff0000-0x000000007effffff]
[ 0.000000] node 0: [mem 0x000000007f000000-0x00000017ffffffff]
[ 0.000000] Initmem setup node 0 [mem
0x0000000000200000-0x00000017ffffffff]
[ 0.000000] On node 0 totalpages: 25145296
[ 0.000000] DMA32 zone: 16376 pages used for memmap
[ 0.000000] DMA32 zone: 0 pages reserved
[ 0.000000] DMA32 zone: 1028048 pages, LIFO batch:31
[ 0.000000] Normal zone: 376832 pages used for memmap
[ 0.000000] Normal zone: 24117248 pages, LIFO batch:31

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
---
mm/memblock.c | 33 +++++++++++++++++++++++++++------
1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 077ca62..46cb6be 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1144,28 +1144,49 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
{
struct memblock_type *type = &memblock.memory;
+ struct memblock_region *regions = type->regions;
unsigned int right = type->cnt;
unsigned int mid, left = 0;
+ unsigned long start_pfn, end_pfn, next_start_pfn;
phys_addr_t addr = PFN_PHYS(++pfn);
+ static int early_region_idx __initdata_memblock = -1;

+ /* fast path, return pfn+1 if next pfn is in the same region */
+ if (early_region_idx != -1) {
+ start_pfn = PFN_DOWN(regions[early_region_idx].base);
+ end_pfn = PFN_DOWN(regions[early_region_idx].base +
+ regions[early_region_idx].size);
+
+ if (pfn >= start_pfn && pfn < end_pfn)
+ return pfn;
+
+ early_region_idx++;
+ next_start_pfn = PFN_DOWN(regions[early_region_idx].base);
+
+ if (pfn >= end_pfn && pfn <= next_start_pfn)
+ return next_start_pfn;
+ }
+
+ /* slow path, do the binary searching */
do {
mid = (right + left) / 2;

- if (addr < type->regions[mid].base)
+ if (addr < regions[mid].base)
right = mid;
- else if (addr >= (type->regions[mid].base +
- type->regions[mid].size))
+ else if (addr >= (regions[mid].base + regions[mid].size))
left = mid + 1;
else {
- /* addr is within the region, so pfn is valid */
+ early_region_idx = mid;
return pfn;
}
} while (left < right);

if (right == type->cnt)
return -1UL;
- else
- return PHYS_PFN(type->regions[right].base);
+
+ early_region_idx = right;
+
+ return PHYS_PFN(regions[early_region_idx].base);
}
EXPORT_SYMBOL(memblock_next_valid_pfn);
#endif /*CONFIG_HAVE_MEMBLOCK_PFN_VALID*/
--
1.8.3.1
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