linux-kernel - Re: [PATCH v2 3/3] sched: increase SCHED_LOAD

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Message-ID: <20110518182605.GC25881@elte.hu>
Date:	Wed, 18 May 2011 20:26:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Nikhil Rao <ncrao@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Stephan Barwolf <stephan.baerwolf@...ilmenau.de>
Subject: Re: [PATCH v2 3/3] sched: increase SCHED_LOAD_SCALE resolution


* Nikhil Rao <ncrao@...gle.com> wrote:

>  /*
> - * Increase resolution of nice-level calculations:
> + * Increase resolution of nice-level calculations for 64-bit architectures.
>   */
> -#define SCHED_LOAD_SHIFT	10
> +#if BITS_PER_LONG > 32
> +#define SCHED_LOAD_RESOLUTION	10
> +#define scale_load(w)		(w << SCHED_LOAD_RESOLUTION)
> +#define scale_load_down(w)	(w >> SCHED_LOAD_RESOLUTION)
> +#else
> +#define SCHED_LOAD_RESOLUTION	0
> +#define scale_load(w)		w
> +#define scale_load_down(w)	w
> +#endif

Please also be a bit more verbose in the comment above why we treat 64-bit 
architectures differently - it's not obvious.

Thanks,

	Ingo
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