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authorWei Yang <richard.weiyang@linux.alibaba.com>2020-08-07 09:25:48 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 21:33:29 +0300
commitd93d5ab9ca01e24efc6add60371b0d5684b5c146 (patch)
treea7a5200b015b9da4e84b03e6d51cfe006abbb88f /mm/page_alloc.c
parent399b795b7a80bf703aae56fa0b66fd1949ca1fd9 (diff)
downloadlinux-d93d5ab9ca01e24efc6add60371b0d5684b5c146.tar.xz
mm/page_alloc.c: simplify pageblock bitmap access
Due to commit e58469bafd05 ("mm: page_alloc: use word-based accesses for get/set pageblock bitmaps"), pageblock bitmap is accessed with word-based access. This operation could be simplified a little. Intuitively, if we want to get a bit range [start_idx, end_idx] in a word, we can do like this: mask = (1 << (end_bitidx - start_bitidx + 1)) - 1; ret = (word >> start_idx) & mask; And also if we want to set a bit range [start_idx, end_idx] with flags, we can do the same by just shift start_bitidx. By doing so we reduce some instructions for these two helper functions: Before Patched set_pfnblock_flags_mask 209 198(-5%) get_pfnblock_flags_mask 101 87(-13%) Since the syntax is changed a little, we need to check the whole 4-bit migrate_type instead of part of it. Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Link: http://lkml.kernel.org/r/20200623124201.8199-3-richard.weiyang@linux.alibaba.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c13
1 files changed, 6 insertions, 7 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6c524fb76b31..e1fdca9ef4e9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -489,8 +489,7 @@ static __always_inline unsigned long __get_pfnblock_flags_mask(struct page *page
bitidx &= (BITS_PER_LONG-1);
word = bitmap[word_bitidx];
- bitidx += end_bitidx;
- return (word >> (BITS_PER_LONG - bitidx - 1)) & mask;
+ return (word >> bitidx) & mask;
}
unsigned long get_pfnblock_flags_mask(struct page *page, unsigned long pfn,
@@ -532,9 +531,8 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
- bitidx += end_bitidx;
- mask <<= (BITS_PER_LONG - bitidx - 1);
- flags <<= (BITS_PER_LONG - bitidx - 1);
+ mask <<= bitidx;
+ flags <<= bitidx;
word = READ_ONCE(bitmap[word_bitidx]);
for (;;) {
@@ -551,8 +549,9 @@ void set_pageblock_migratetype(struct page *page, int migratetype)
migratetype < MIGRATE_PCPTYPES))
migratetype = MIGRATE_UNMOVABLE;
- set_pageblock_flags_group(page, (unsigned long)migratetype,
- PB_migrate, PB_migrate_end);
+ set_pfnblock_flags_mask(page, (unsigned long)migratetype,
+ page_to_pfn(page), PB_migrate_end,
+ MIGRATETYPE_MASK);
}
#ifdef CONFIG_DEBUG_VM