From: Dennis Zhou <dennis@kernel.org>
To: Yury Norov <yury.norov@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-mmc@vger.kernel.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Tejun Heo <tj@kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
Ulf Hansson <ulf.hansson@linaro.org>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/4] mm/percpu: micro-optimize pcpu_is_populated()
Date: Wed, 21 Jul 2021 21:07:08 +0000 [thread overview]
Message-ID: <YPiMUF/sYpjPSADv@google.com> (raw)
In-Reply-To: <20210719021755.883182-2-yury.norov@gmail.com>
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
next prev parent reply other threads:[~2021-07-21 21:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 2:17 [PATCH v2 0/4] bitmap: unify for_each_bit() macros Yury Norov
2021-07-19 2:17 ` [PATCH 1/4] mm/percpu: micro-optimize pcpu_is_populated() Yury Norov
2021-07-21 21:07 ` Dennis Zhou [this message]
2021-07-19 2:17 ` [PATCH 2/4] bitmap: unify find_bit operations Yury Norov
2021-07-21 21:12 ` Dennis Zhou
2021-08-04 10:07 ` Ulf Hansson
2021-08-11 7:38 ` Wolfram Sang
2021-08-12 1:23 ` Yury Norov
2021-07-19 2:17 ` [PATCH 3/4] lib: bitmap: add performance test for bitmap_print_to_pagebuf Yury Norov
2021-07-19 2:17 ` [PATCH 4/4] vsprintf: rework bitmap_list_string Yury Norov
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