linux-kernel - Re: [patch 1/2] round

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Date:	Tue, 10 Oct 2006 11:56:52 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [patch 1/2] round_jiffies infrastructure

On Tue, 10 Oct 2006 18:03:30 +0200
Arjan van de Ven <arjan@...ux.intel.com> wrote:

> @@ -80,6 +80,56 @@ tvec_base_t boot_tvec_bases;
>  EXPORT_SYMBOL(boot_tvec_bases);
>  static DEFINE_PER_CPU(tvec_base_t *, tvec_bases) = &boot_tvec_bases;
>  
> +unsigned long __round_jiffies(unsigned long T, int CPU)
> +{
> +	int rem;
> +	int original  = T;
> +	rem = T % HZ;
> +	if (rem < HZ/4)
> +		T = T - rem;
> +	else
> +		T = T - rem + HZ;
> +	/* we don't want all cpus firing at once hitting the same lock/memory */
> +	T += CPU * 3;
> +	if (T <= jiffies) /* rounding ate our timeout entirely */
> +		return original;
> +	return T;
> +}
> +EXPORT_SYMBOL_GPL(__round_jiffies);
> +

c'mon Arjan.  If we're going to create new, kernel-wide,
exported-to-modules infrastructure then it deserves slightly more than zero
documentation.

Some commentary explaining/justifying the magic numbers in there would be
useful too.  The HZ/4, the cpu*3.

And coding style too, please: consistent spacing around arithmetic
operators, variables are lower case, constants are upper case.
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