Commit b92df1de authored by Paul Burton's avatar Paul Burton Committed by Linus Torvalds

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: default avatarPaul Burton <>
Tested-by: default avatarJames Hartley <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 7f354a54
......@@ -203,6 +203,7 @@ int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
unsigned long *end_pfn);
void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
unsigned long *out_end_pfn, int *out_nid);
unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
* for_each_mem_pfn_range - early memory pfn range iterator
......@@ -1105,6 +1105,31 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
*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 +
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
......@@ -5103,8 +5103,17 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
if (context != MEMMAP_EARLY)
goto not_early;
if (!early_pfn_valid(pfn))
if (!early_pfn_valid(pfn)) {
* Skip to the pfn preceding the next valid one (or
* 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, end_pfn) - 1;
if (!early_pfn_in_nid(pfn, nid))
if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
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