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Commit b92df1de authored by Paul Burton's avatar Paul Burton Committed by Linus Torvalds
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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: default avatarPaul Burton <paul.burton@imgtec.com>
Tested-by: default avatarJames Hartley <james.hartley@imgtec.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7f354a54

include/linux/memblock.h

+1 −0
Original line number Diff line number Diff line
@@ -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

mm/memblock.c

+25 −0
Original line number Diff line number Diff line
@@ -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 +

				  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

mm/page_alloc.c

+10 −1
Original line number Diff line number Diff line
@@ -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)) {

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP

			/*

			 * 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;

#endif

			continue;

		}

		if (!early_pfn_in_nid(pfn, nid))

			continue;

		if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))