linux-kernel - Re: [PATCH v7 3/3] nl80211/mac80211: Report signal average

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Message-ID: <AANLkTimoogSLAipNy=njGtHypqBQSk=usDmXut=KN9TM@mail.gmail.com>
Date:	Wed, 17 Nov 2010 18:11:18 -0500
From:	Bob Copeland <me@...copeland.com>
To:	Bruno Randolf <br1@...fach.org>
Cc:	Johannes Berg <johannes@...solutions.net>, Jouni Malinen <j@...fi>,
	linville@...driver.com, randy.dunlap@...cle.com,
	peterz@...radead.org, blp@...stanford.edu,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lars_Ericsson@...ia.com, stefanr@...6.in-berlin.de,
	kosaki.motohiro@...fujitsu.com, akpm@...ux-foundation.org,
	kevin.granade@...il.com
Subject: Re: [PATCH v7 3/3] nl80211/mac80211: Report signal average

On Wed, Nov 17, 2010 at 11:16 AM, Johannes Berg
<johannes@...solutions.net> wrote:
> On Wed, 2010-11-17 at 17:28 +0900, Bruno Randolf wrote:
>> I understand that this could be more efficient, but if it matters or not -
>> honestly, I don't know. Can a more knowledgeable person than me comment on
>> this?
>
> Yes, it does matter -- think of an embedded MIPS board running at 500MHz
> and trying to push 11n speeds.

I assume the number of samples (weight) is the more
important tunable.  One option is you can require factor
to be a power of two that is much larger than weight,
then at least you can store factor/weight precomputed
and multiply by it instead of doing a divide in ewma_add.
Then ewma_get can also just be a shift as well.

-- 
Bob Copeland %% www.bobcopeland.com
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