[025/131] mm: memmap_init: iterate over memblock regions rather that check each PFN

Commit Message

Andrew Morton June 3, 2020, 10:57 p.m. UTC

From: Baoquan He <[e-mail]>
Subject: mm: memmap_init: iterate over memblock regions rather that check each PFN

When called during boot the memmap_init_zone() function checks if each PFN
is valid and actually belongs to the node being initialized using
early_pfn_valid() and early_pfn_in_nid().

Each such check may cost up to O(log(n)) where n is the number of memory
banks, so for large amount of memory overall time spent in early_pfn*()
becomes substantial.

Since the information is anyway present in memblock, we can iterate over
memblock memory regions in memmap_init() and only call memmap_init_zone()
for PFN ranges that are know to be valid and in the appropriate node.

[[e-mail]: fix a compilation warning from Clang]
  Link: http://lkml.kernel.org/r/[e-mail]
[[e-mail]: fix the incorrect hole in fast_isolate_freepages()]
  Link: http://lkml.kernel.org/r/[e-mail]
  Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Baoquan He <[e-mail]>
Signed-off-by: Mike Rapoport <[e-mail]>
Tested-by: Hoan Tran <[e-mail]>	[arm64]
Cc: Brian Cain <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Greentime Hu <[e-mail]>
Cc: Greg Ungerer <[e-mail]>
Cc: Guan Xuetao <[e-mail]>
Cc: Guo Ren <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Helge Deller <[e-mail]>
Cc: "James E.J. Bottomley" <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Ley Foon Tan <[e-mail]>
Cc: Mark Salter <[e-mail]>
Cc: Matt Turner <[e-mail]>
Cc: Max Filippov <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Michal Simek <[e-mail]>
Cc: Nick Hu <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Richard Weinberger <[e-mail]>
Cc: Rich Felker <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Stafford Horne <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Tony Luck <[e-mail]>
Cc: Vineet Gupta <[e-mail]>
Cc: Yoshinori Sato <[e-mail]>
Cc: Qian Cai <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/compaction.c |    4 +++-
 mm/page_alloc.c |   43 ++++++++++++++++---------------------------
 2 files changed, 19 insertions(+), 28 deletions(-)

Patch

--- a/mm/compaction.c~mm-memmap_init-iterate-over-memblock-regions-rather-that-check-each-pfn
+++ a/mm/compaction.c
@@ -1409,7 +1409,9 @@  fast_isolate_freepages(struct compact_co
 				cc->free_pfn = highest;
 			} else {
 				if (cc->direct_compaction && pfn_valid(min_pfn)) {
-					page = pfn_to_page(min_pfn);
+					page = pageblock_pfn_to_page(min_pfn,
+						pageblock_end_pfn(min_pfn),
+						cc->zone);
 					cc->free_pfn = min_pfn;
 				}
 			}
--- a/mm/page_alloc.c~mm-memmap_init-iterate-over-memblock-regions-rather-that-check-each-pfn
+++ a/mm/page_alloc.c
@@ -5951,23 +5951,6 @@  overlap_memmap_init(unsigned long zone,
 	return false;
 }
 
-#ifdef CONFIG_SPARSEMEM
-/* Skip PFNs that belong to non-present sections */
-static inline __meminit unsigned long next_pfn(unsigned long pfn)
-{
-	const unsigned long section_nr = pfn_to_section_nr(++pfn);
-
-	if (present_section_nr(section_nr))
-		return pfn;
-	return section_nr_to_pfn(next_present_section_nr(section_nr));
-}
-#else
-static inline __meminit unsigned long next_pfn(unsigned long pfn)
-{
-	return pfn++;
-}
-#endif
-
 /*
  * Initially all pages are reserved - free ones are freed
  * up by memblock_free_all() once the early boot process is
@@ -6007,14 +5990,6 @@  void __meminit memmap_init_zone(unsigned
 		 * function.  They do not exist on hotplugged memory.
 		 */
 		if (context == MEMMAP_EARLY) {
-			if (!early_pfn_valid(pfn)) {
-				pfn = next_pfn(pfn);
-				continue;
-			}
-			if (!early_pfn_in_nid(pfn, nid)) {
-				pfn++;
-				continue;
-			}
 			if (overlap_memmap_init(zone, &pfn))
 				continue;
 			if (defer_init(nid, pfn, end_pfn))
@@ -6130,9 +6105,23 @@  static void __meminit zone_init_free_lis
 }
 
 void __meminit __weak memmap_init(unsigned long size, int nid,
-				  unsigned long zone, unsigned long start_pfn)
+				  unsigned long zone,
+				  unsigned long range_start_pfn)
 {
-	memmap_init_zone(size, nid, zone, start_pfn, MEMMAP_EARLY, NULL);
+	unsigned long start_pfn, end_pfn;
+	unsigned long range_end_pfn = range_start_pfn + size;
+	int i;
+
+	for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
+		start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
+		end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
+
+		if (end_pfn > start_pfn) {
+			size = end_pfn - start_pfn;
+			memmap_init_zone(size, nid, zone, start_pfn,
+					 MEMMAP_EARLY, NULL);
+		}
+	}
 }
 
 static int zone_batchsize(struct zone *zone)