[PATCH v2 15/20] mm: memmap_init: iterate over memblock regions rather that check each PFN

Mike Rapoport
2020-04-29T12:11:21Z

From: Baoquan He <bhe@redhat.com>

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.

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
mm/page_alloc.c | 47 ++++++++++++++++-------------------------------
1 file changed, 16 insertions(+), 31 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7f6a3081edb8..8d112defaead 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5939,23 +5939,6 @@ overlap_memmap_init(unsigned long zone, unsigned long *pfn)
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
@@ -5990,19 +5973,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
#endif

for (pfn = start_pfn; pfn < end_pfn; ) {
- /*
- * There can be holes in boot-time mem_map[]s handed to this
- * 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))
@@ -6118,9 +6089,23 @@ static void __meminit zone_init_free_lists(struct zone *zone)
}

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)
--
2.26.1