From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <52028C60.90405@xenomai.org> Date: Wed, 07 Aug 2013 20:05:20 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <1124806E0C09F04A992E69AE2EC7FA3C80A6B1@swexchange01.itk.local> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Problems with running Xenomai on Core i5 List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Matthew Fornero Cc: "xenomai@xenomai.org" On 08/07/2013 05:13 PM, Matthew Fornero wrote: > On Wed, Aug 7, 2013 at 9:38 AM, Tobias Luksch > wrote: >> To me it looks like some power management feature of the CPU is kicking in. I >> have disabled (hopefully) all relevant features in the BIOS (like EISS, >> TurboBoost, Idle Modes, ...) and in the kernel (CPU frequency scaling, ..., >> config file of me latest try is attached), /proc/cpuinfo always shows the same >> frequency. Still I get the behavior described above. > > Hi Tobias, > > What you're describing sounds exactly like C1E kicking in-- there > seems to be a latency penalty when cores exit C1E. This is usually not > exposed in the BIOS power settings (we had to add it to our boards). > Fortunately it can be controlled via MSR and takes effect immediately. > There's a bit in MSR 0x1FC (MSR_IA32_POWER_CTL) that needs to be > cleared. I *believe* it's bit 1, but can't remember. Note that I > believe this MSR is defined per-core, so you'll need to toggle the MSR > on all the cores that you want to disable C1E on (usually all of > them). > > A google search for MSR_IA32_POWER_CTL and C1E should be able to find > some sort of documentation. > > You should be able to tell if it's working using the built-in xenomai > latency test. Run it on an idle (and otherwise well configured) system > for 5-10 minutes and you should see a very noticable difference in > scheduler latency with C1E on and off. IIRC, the C1E can be enabled/disabled with Intel BIOS testing utilities: http://biosbits.org/ -- Gilles.