From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 04 Oct 2011 09:10:11 +0200 From: "Petr Cervenka" References: <20110926090226.9C75AD68@domain.hid>, <20111003103914.8A2B636C@centrum.cz> In-Reply-To: MIME-Version: 1.0 Message-Id: <20111004091011.AE85F1D2@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Xenomai-help] Frequency downscaling of new intel CPU List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: xenomai-help > On Mon, Oct 3, 2011 at 4:39 AM, Petr Cervenka wrote: > > Any ideas that could help me? > What about looking at /proc/cpuinfo while running your system ? If you > see that the speed is not the maximal, indeed, the frequency scaling > system changes the speed of the processor. /proc/cpuinfo shows always full frequency clock (3292.500 MHz) More details: 1) two xenomai tasks are running with 100us period (controlled by externa= l hardware) 2) one task communicates with hardware (receives data via rtnet) and pass= es them by rt_queue to the second task (on another core) 3) second task does some computations and returns processed data to the f= irst task 4) first task sends data to hardware The problem is that during waiting on new data from hw CPU puts itself in= some deeper idle state with lower frequency. A then, when the data are a= vailable, it slowly wakes up to normal state. In other words: computation takes longer time than it takes on older comp= uters (depends on overall CPU load). When some artificial 100% load is running on another core, the computatio= n is as fast as it should be. Petr