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Commit f75fb889 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm, page_alloc: avoid unnecessary zone lookups during pageblock operations 



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: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 754078eb

mm/page_alloc.c

+9 −13
Original line number Diff line number Diff line
@@ -6767,23 +6767,23 @@ 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 */

}
@@ -6801,14 +6801,12 @@ 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);
@@ -6830,20 +6828,18 @@ 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);