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* [PATCH] lib: micro-optimization for __bitmap_complement()
@ 2018-04-11 14:59 Yury Norov
  2018-04-20 13:43 ` Yury Norov
  0 siblings, 1 reply; 2+ messages in thread
From: Yury Norov @ 2018-04-11 14:59 UTC (permalink / raw)
  To: Andrew Morton, Matthew Wilcox, Rasmus Villemoes, linux-kernel; +Cc: Yury Norov

Use BITS_TO_LONGS() macro to avoid calculation of reminder
(bits % BITS_PER_LONG) On ARM64 it saves 5 instruction for function -
16 before and 11 after.

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
---
 lib/bitmap.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index c82c61b66e16..7adc10074cff 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -62,12 +62,9 @@ EXPORT_SYMBOL(__bitmap_equal);
 
 void __bitmap_complement(unsigned long *dst, const unsigned long *src, unsigned int bits)
 {
-	unsigned int k, lim = bits/BITS_PER_LONG;
+	unsigned int k, lim = BITS_TO_LONGS(bits);
 	for (k = 0; k < lim; ++k)
 		dst[k] = ~src[k];
-
-	if (bits % BITS_PER_LONG)
-		dst[k] = ~src[k];
 }
 EXPORT_SYMBOL(__bitmap_complement);
 
-- 
2.14.1

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] lib: micro-optimization for __bitmap_complement()
  2018-04-11 14:59 [PATCH] lib: micro-optimization for __bitmap_complement() Yury Norov
@ 2018-04-20 13:43 ` Yury Norov
  0 siblings, 0 replies; 2+ messages in thread
From: Yury Norov @ 2018-04-20 13:43 UTC (permalink / raw)
  To: Andrew Morton, Matthew Wilcox, Rasmus Villemoes, linux-kernel

Ping?

On Wed, Apr 11, 2018 at 05:59:14PM +0300, Yury Norov wrote:
> Use BITS_TO_LONGS() macro to avoid calculation of reminder
> (bits % BITS_PER_LONG) On ARM64 it saves 5 instruction for function -
> 16 before and 11 after.
> 
> Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
> ---
>  lib/bitmap.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index c82c61b66e16..7adc10074cff 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -62,12 +62,9 @@ EXPORT_SYMBOL(__bitmap_equal);
>  
>  void __bitmap_complement(unsigned long *dst, const unsigned long *src, unsigned int bits)
>  {
> -	unsigned int k, lim = bits/BITS_PER_LONG;
> +	unsigned int k, lim = BITS_TO_LONGS(bits);
>  	for (k = 0; k < lim; ++k)
>  		dst[k] = ~src[k];
> -
> -	if (bits % BITS_PER_LONG)
> -		dst[k] = ~src[k];
>  }
>  EXPORT_SYMBOL(__bitmap_complement);
>  
> -- 
> 2.14.1

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2018-04-11 14:59 [PATCH] lib: micro-optimization for __bitmap_complement() Yury Norov
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