2023-05-06 09:01:59

by ye.xingchen

Subject: [PATCH] arm64: mm: use bitmap_zero() API

From: Ye Xingchen <[email protected]>

bitmap_zero() is faster than bitmap_clear(), so use bitmap_zero()
instead of bitmap_clear().

Signed-off-by: Ye Xingchen <[email protected]>
---
arch/arm64/mm/context.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index e1e0dca01839..ed0bf7f8e8ce 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -95,7 +95,7 @@ static void set_reserved_asid_bits(void)
else if (arm64_kernel_unmapped_at_el0())
set_kpti_asid_bits(asid_map);
else
- bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
+ bitmap_zero(asid_map, NUM_USER_ASIDS);
}

#define asid_gen_match(asid) \
--
2.25.1

2023-05-16 13:45:34

by Will Deacon

Subject: Re: [PATCH] arm64: mm: use bitmap_zero() API

On Sat, May 06, 2023 at 04:36:31PM +0800, [email protected] wrote:
> From: Ye Xingchen <[email protected]>
>
> bitmap_zero() is faster than bitmap_clear(), so use bitmap_zero()
> instead of bitmap_clear().

Is it? Don't these both boil down to:

memset(asid_map, 0, NUM_USER_ASIDS / 8)

?

Will

> ---
> arch/arm64/mm/context.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
> index e1e0dca01839..ed0bf7f8e8ce 100644
> --- a/arch/arm64/mm/context.c
> +++ b/arch/arm64/mm/context.c
> @@ -95,7 +95,7 @@ static void set_reserved_asid_bits(void)
> else if (arm64_kernel_unmapped_at_el0())
> set_kpti_asid_bits(asid_map);
> else
> - bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
> + bitmap_zero(asid_map, NUM_USER_ASIDS);
> }
>
> #define asid_gen_match(asid) \
> --
> 2.25.1