From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: spi_async and heavy CPU occupation by ksoftirqd Date: Thu, 9 Aug 2007 08:23:29 -0700 Message-ID: <200708090823.29708.david-b@pacbell.net> References: <46B97D01.5000208@dave-tech.it> <200708080927.36737.david-b@pacbell.net> <46BB1F10.3030608@dave-tech.it> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: llandre Return-path: In-Reply-To: <46BB1F10.3030608-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On Thursday 09 August 2007, llandre wrote: > > At a first glance, I wonder if you're not spending too much time > > in the spi_imx "pump_transfers" tasklet. =A0I have no idea how well > > tuned that driver is... > = > Hmmm ... how do you suggest me to investigate around this tasklet? Do I = > need to use the toggling pin technique That seems to be the most precise tool you have, unless you have access to the JTAG-style hardware tools giving access to the on-chip instruction trace buffers found in many ARMs. > or does the kernel provides some = > tools to do that? Could oprofile come to help? Statistical profiling probably wouldn't help. I'm not sure that anything like gprof is working in the kernel. Folk that I know have done that level analysis tend to rely on hardware trace tools. > > I'd expect that using spi_sync() wouldn't save much, but it might > > be worth verifying that. > > Initially my driver used spi_sync. When I realized the huge CPU = > occupation I modified it in order to use spi_async instead but, again, = > nothing changed. And that should have been a HUGE clue that the way you were calling it wasn't a factor at all. = - Dave = ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/