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Subject[PATCH 09/13] mm: meminit: Minimise number of pfn->page lookups during initialisation
Date
Deferred struct page initialisation is using pfn_to_page() on every PFN
unnecessarily. This patch minimises the number of lookups and scheduler
checks.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/page_alloc.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index dfe63a3c3816..839e4c73ce6d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1089,6 +1089,7 @@ void __defermem_init deferred_init_memmap(int nid)

for_each_mem_pfn_range(i, nid, &walk_start, &walk_end, NULL) {
unsigned long pfn, end_pfn;
+ struct page *page = NULL;

end_pfn = min(walk_end, zone_end_pfn(zone));
pfn = first_init_pfn;
@@ -1098,13 +1099,32 @@ void __defermem_init deferred_init_memmap(int nid)
pfn = zone->zone_start_pfn;

for (; pfn < end_pfn; pfn++) {
- struct page *page;
-
- if (!pfn_valid(pfn))
+ if (!pfn_valid_within(pfn))
continue;

- if (!meminit_pfn_in_nid(pfn, nid, &nid_init_state))
+ /*
+ * Ensure pfn_valid is checked every
+ * MAX_ORDER_NR_PAGES for memory holes
+ */
+ if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
+ if (!pfn_valid(pfn)) {
+ page = NULL;
+ continue;
+ }
+ }
+
+ if (!meminit_pfn_in_nid(pfn, nid, &nid_init_state)) {
+ page = NULL;
continue;
+ }
+
+ /* Minimise pfn page lookups and scheduler checks */
+ if (page && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0) {
+ page++;
+ } else {
+ page = pfn_to_page(pfn);
+ cond_resched();
+ }

if (page->flags) {
VM_BUG_ON(page_zone(page) != zone);
@@ -1113,7 +1133,6 @@ void __defermem_init deferred_init_memmap(int nid)

__init_single_page(page, pfn, zid, nid);
__free_pages_boot_core(page, pfn, 0);
- cond_resched();
}
first_init_pfn = max(end_pfn, first_init_pfn);
}
--
2.1.2


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