[PATCH 07/24] mm, page_alloc: Avoid unnecessary zone lookups during pageblock operations

From: Mel Gorman
Date: Tue Apr 12 2016 - 06:13:17 EST


Pageblocks have an associated bitmap to store migrate types and whether
the pageblock should be skipped during compaction. The bitmap may be
associated with a memory section or a zone but the zone is looked up
unconditionally. The compiler should optimise this away automatically so
this is a cosmetic patch only in many cases.

Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ab16560b76e6..d00847bb1612 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6759,23 +6759,23 @@ void *__init alloc_large_system_hash(const char *tablename,
}

/* Return a pointer to the bitmap storing bits affecting a block of pages */
-static inline unsigned long *get_pageblock_bitmap(struct zone *zone,
+static inline unsigned long *get_pageblock_bitmap(struct page *page,
unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
return __pfn_to_section(pfn)->pageblock_flags;
#else
- return zone->pageblock_flags;
+ return page_zone(page)->pageblock_flags;
#endif /* CONFIG_SPARSEMEM */
}

-static inline int pfn_to_bitidx(struct zone *zone, unsigned long pfn)
+static inline int pfn_to_bitidx(struct page *page, unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
pfn &= (PAGES_PER_SECTION-1);
return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
#else
- pfn = pfn - round_down(zone->zone_start_pfn, pageblock_nr_pages);
+ pfn = pfn - round_down(page_zone(page)->zone_start_pfn, pageblock_nr_pages);
return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
#endif /* CONFIG_SPARSEMEM */
}
@@ -6793,14 +6793,12 @@ unsigned long get_pfnblock_flags_mask(struct page *page, unsigned long pfn,
unsigned long end_bitidx,
unsigned long mask)
{
- struct zone *zone;
unsigned long *bitmap;
unsigned long bitidx, word_bitidx;
unsigned long word;

- zone = page_zone(page);
- bitmap = get_pageblock_bitmap(zone, pfn);
- bitidx = pfn_to_bitidx(zone, pfn);
+ bitmap = get_pageblock_bitmap(page, pfn);
+ bitidx = pfn_to_bitidx(page, pfn);
word_bitidx = bitidx / BITS_PER_LONG;
bitidx &= (BITS_PER_LONG-1);

@@ -6822,20 +6820,18 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
unsigned long end_bitidx,
unsigned long mask)
{
- struct zone *zone;
unsigned long *bitmap;
unsigned long bitidx, word_bitidx;
unsigned long old_word, word;

BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);

- zone = page_zone(page);
- bitmap = get_pageblock_bitmap(zone, pfn);
- bitidx = pfn_to_bitidx(zone, pfn);
+ bitmap = get_pageblock_bitmap(page, pfn);
+ bitidx = pfn_to_bitidx(page, pfn);
word_bitidx = bitidx / BITS_PER_LONG;
bitidx &= (BITS_PER_LONG-1);

- VM_BUG_ON_PAGE(!zone_spans_pfn(zone, pfn), page);
+ VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);

bitidx += end_bitidx;
mask <<= (BITS_PER_LONG - bitidx - 1);
--
2.6.4