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authorPaul Burton <paul.burton@imgtec.com>2017-02-22 15:44:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-22 16:41:29 -0800
commitb92df1de5d289c0b5d653e72414bf0850b8511e0 (patch)
tree6604acfffcd8f9ca58499f892531bd08dc117fea /mm/page_alloc.c
parent7f354a548d1cb6bb01b6ee74aee9264aa152f1ec (diff)
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>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 05c0a59323bd..6da3169d3750 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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))