linux-kernel - Re: [PATCH v3] Add generic exponentially weighted moving average (EWMA) function

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Message-Id: <20101021192658.C8EE.A69D9226@jp.fujitsu.com>
Date:	Thu, 21 Oct 2010 19:31:47 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Bruno Randolf <br1@...fach.org>
Cc:	kosaki.motohiro@...fujitsu.com, randy.dunlap@...cle.com,
	akpm@...ux-foundation.org, kevin.granade@...il.com,
	Lars_Ericsson@...ia.com, blp@...stanford.edu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Add generic exponentially weighted moving average (EWMA) function

Hi

I'm plaing this a bit and I have to say this doesn't works as I expected
because ewma_init() has very easy confusable.

so, I have one request.


> +/**
> + * ewma_init() - Initialize EWMA parameters
> + * @avg: Average structure
> + * @factor: Factor to use for the scaled up internal value. The maximum value
> + *	of averages can be UINT_MAX/(factor*weight).
> + * @weight: Exponential weight, or decay rate. This defines how fast the
> + * 	influence of older values decreases. Has to be bigger than 1.
> + *
> + * Initialize the EWMA parameters for a given struct ewma @avg.
> + */
> +struct ewma*
> +ewma_init(struct ewma *avg, const unsigned int factor,
> +	  const unsigned int weight)
> +{
> +	WARN_ON(weight <= 1 || factor == 0);
> +	avg->weight = weight;
> +	avg->factor = factor;
> +	return avg;
> +}
> +EXPORT_SYMBOL(ewma_init);

Please initalize avg->internal too.


and nit, I don't understand what you intend by 'const unsigned int'. I think
we can remove this const safely. it's more easy readable.




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