mm: page_alloc: skip over regions of invalid pfns where possible
When using a sparse memory model memmap_init_zone() when invoked with
the MEMMAP_EARLY context will skip over pages which aren't valid - ie.
which aren't in a populated region of the sparse memory map. However if
the memory map is extremely sparse then it can spend a long time
linearly checking each PFN in a large non-populated region of the memory
map & skipping it in turn.
When CONFIG_HAVE_MEMBLOCK_NODE_MAP is enabled, we have sufficient
information to quickly discover the next valid PFN given an invalid one
by searching through the list of memory regions & skipping forwards to
the first PFN covered by the memory region to the right of the
non-populated region. Implement this in order to speed up
memmap_init_zone() for systems with extremely sparse memory maps.
James said "I have tested this patch on a virtual model of a Samurai CPU
with a sparse memory map. The kernel boot time drops from 109 to
62 seconds. "
Link: http://lkml.kernel.org/r/20161125185518.29885-1-paul.burton@imgtec.com
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Tested-by: James Hartley <james.hartley@imgtec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memblock.c b/mm/memblock.c
index 7608bc3..a476d28 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1105,6 +1105,31 @@
*out_nid = r->nid;
}
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
+ unsigned long max_pfn)
+{
+ struct memblock_type *type = &memblock.memory;
+ unsigned int right = type->cnt;
+ unsigned int mid, left = 0;
+ phys_addr_t addr = PFN_PHYS(pfn + 1);
+
+ 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 + 1 is valid */
+ return min(pfn + 1, max_pfn);
+ }
+ } while (left < right);
+
+ return min(PHYS_PFN(type->regions[right].base), max_pfn);
+}
+
/**
* memblock_set_node - set node ID on memblock regions
* @base: base of area to set node ID for