Return-path: Received: from static-ip-62-75-166-246.inaddr.intergenia.de ([62.75.166.246]:48053 "EHLO vs166246.vserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752505AbXBDTHm (ORCPT ); Sun, 4 Feb 2007 14:07:42 -0500 From: Michael Buesch To: "Jon Smirl" Subject: Re: SoftMAC vs FullMAC Date: Sun, 4 Feb 2007 20:07:29 +0100 Cc: "Pavel Roskin" , linux-wireless@vger.kernel.org References: <9e4733910702040922n63736d27h7ab027dc90ae8989@mail.gmail.com> <20070204123048.4bhesocg4kosgscg@webmail.spamcop.net> <9e4733910702041031i5edd6dfeq7f8c5179fee5e00e@mail.gmail.com> In-Reply-To: <9e4733910702041031i5edd6dfeq7f8c5179fee5e00e@mail.gmail.com> MIME-Version: 1.0 Message-Id: <200702042007.29357.mb@bu3sch.de> Content-Type: text/plain; charset="iso-8859-1" Sender: linux-wireless-owner@vger.kernel.org List-ID: On Sunday 04 February 2007 19:31, Jon Smirl wrote: > On 2/4/07, Pavel Roskin wrote: > > In fact, Atheros chips are not that intelligent to be treated as FullMAC, but > > going to d80211 removes many chip specific features. > > What types of features are removed? For example Atheros turbo mode can > be treated like another PHY layer implementation. > > If it is just off-loading the implementation of standard behavior then > we may actually be better off ignoring this capability and > implementing the standard behavior in the host. > > It's not even clear to me that doing encryption is a wireless > co-processor is a win. It is almost certain that the host can perform > the same algorithms many times faster that an embedded wireless > processor. Moving encryption onto the host reduces the latency of the > connection. If creating and uploading the keys to the device is less work than doing crypto in software, then it is clearly a win. And that _is_ the case for bcm43xx (at least. I don't know about other devices' hwcrypto capabilities). Doing less on the CPU and more in hw is always a win. I'm not sure how you can say that you're not sure it is. ;) Additionally, doing crypto in the RX path (tasklet context) is not really optimal, from a latency point of view. But you can test it yourself. Enable/disable hwcrypto and watch how CPU load in "top" reacts. I did a quick test on my powerbook and software interrupt load decreases from about 30% to about 10% when switching from swcrypto to hwcrypto. I'd call that a significant win. And this 20% decrease is just the RX path. TX is done in process context (I think). -- Greetings Michael.