diff options
| author | Wei Yang <richard.weiyang@linux.alibaba.com> | 2020-08-06 23:25:48 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-07 11:33:29 -0700 |
| commit | d93d5ab9ca01e24efc6add60371b0d5684b5c146 (patch) | |
| tree | a7a5200b015b9da4e84b03e6d51cfe006abbb88f /mm/page_alloc.c | |
| parent | 399b795b7a80bf703aae56fa0b66fd1949ca1fd9 (diff) | |
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.c | 13 |
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 |