lkml.org 
[lkml]   [2021]   [Jul]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] mm/percpu: micro-optimize pcpu_is_populated()
Hello,

On Sun, Jul 18, 2021 at 07:17:52PM -0700, Yury Norov wrote:
> 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>
> ---
> mm/percpu.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 7f2e0151c4e2..25461571dcc5 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -1071,17 +1071,18 @@ 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;
> }
>
> --
> 2.30.2
>

Sorry for the delay.

Acked-by: Dennis Zhou <dennis@kernel.org>

Thanks,
Dennis

\
 
 \ /
  Last update: 2021-07-21 23:10    [W:0.061 / U:0.372 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site