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mm/percpu: micro-optimize pcpu_is_populated() 

bitmap_next_clear_region() calls find_next_zero_bit() and find_next_bit()
sequentially to find a range of clear bits. In case of pcpu_is_populated()
there's a chance to return earlier if bitmap has all bits set.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Dennis Zhou <dennis@kernel.org>
This commit is contained in:
Yury Norov 2021-08-14 14:17:10 -07:00
parent 749443de8d
commit 801a57365f
1 changed files with 8 additions and 7 deletions
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15
mm/percpu.c
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@ -1070,17 +1070,18 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
int *next_off)
{
unsigned int page_start, page_end, rs, re;
unsigned int start, end;
page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
rs = page_start;
bitmap_next_clear_region(chunk->populated, &rs, &re, page_end);
if (rs >= page_end)
start = find_next_zero_bit(chunk->populated, end, start);
if (start >= end)
return true;
*next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE;
end = find_next_bit(chunk->populated, end, start + 1);
*next_off = end * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE;
return false;
}