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Date:   Fri, 20 Apr 2018 16:43:05 +0300
From:   Yury Norov <ynorov@caviumnetworks.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] lib: micro-optimization for __bitmap_complement()
Message-ID: <20180420134305.azmvwwmgi7avga7s@yury-thinkpad>
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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