linux-kernel - Re: [PATCH 1/1] core-kernel: use multiply instead of shifts in hash

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Date:	Tue, 10 Jul 2012 17:35:17 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Andrew Hunter <ahh@...gle.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] core-kernel: use multiply instead of shifts in hash_64

On 03.07.2012 00:25, Andrew Hunter wrote:
> diff --git a/include/linux/hash.h b/include/linux/hash.h
> index b80506b..daabc3d 100644
> --- a/include/linux/hash.h
> +++ b/include/linux/hash.h
> @@ -34,7 +34,9 @@
>  static inline u64 hash_64(u64 val, unsigned int bits)
>  {
>  	u64 hash = val;
> -
> +#if BITS_PER_LONG == 64
> +	hash *= GOLDEN_RATIO_PRIME_64;
> +#else
>  	/*  Sigh, gcc can't optimise this alone like it does for 32 bits. */

Hmm.  Does this comment make sense here now?

Thanks,

/mjt
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