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Date: Wed, 17 Nov 2010 18:11:18 -0500
Message-ID: <AANLkTimoogSLAipNy=njGtHypqBQSk=usDmXut=KN9TM@mail.gmail.com>
Subject: Re: [PATCH v7 3/3] nl80211/mac80211: Report signal average
From: Bob Copeland <me@bobcopeland.com>
To: Bruno Randolf <br1@einfach.org>
Cc: Johannes Berg <johannes@sipsolutions.net>, Jouni Malinen <j@w1.fi>,
	linville@tuxdriver.com, randy.dunlap@oracle.com,
	peterz@infradead.org, blp@cs.stanford.edu,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
	Lars_Ericsson@telia.com, stefanr@s5r6.in-berlin.de,
	kosaki.motohiro@jp.fujitsu.com, akpm@linux-foundation.org,
	kevin.granade@gmail.com
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On Wed, Nov 17, 2010 at 11:16 AM, Johannes Berg
<johannes@sipsolutions.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