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mm: page_alloc: skip over regions of invalid pfns where possible

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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/[email protected]
Signed-off-by: Paul Burton <[email protected]>
Tested-by: James Hartley <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Paul Burton 2017-02-22 15:44:53 -08:00 • committed by Linus Torvalds
commit b92df1de5d
3 changed files with 36 additions and 1 deletions
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25
mm/memblock.c
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@ -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