From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tobias Luksch Date: Wed, 11 Dec 2013 16:04:29 +0000 Message-ID: <1124806E0C09F04A992E69AE2EC7FA3CB1B138@swexchange01.itk.local> References: <529F1913.4030604@xenomai.org> <529F1974.60900@xenomai.org> <529F2BED.2030403@xenomai.org> <529F5254.8060501@xenomai.org> <529F69AD.6060003@xenomai.org> <52A05ED2.9050003@xenomai.org> <52A5E155.2040303@xenomai.org> <4453D563-1D0B-4C5E-BCF1-3E2E8068B514@open.ac.uk> <20131211145136.GL20884@csclub.uwaterloo.ca> In-Reply-To: <20131211145136.GL20884@csclub.uwaterloo.ca> Content-Language: de-DE Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [Xenomai] latency spikes under load List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Lennart Sorensen , Kurijn Buys Cc: "Xenomai@xenomai.org" > > On Wed, Dec 11, 2013 at 02:23:38PM +0000, Kurijn Buys wrote: > > I enabled APIC, and the latency peaks at 16us only now, and even less w= ith > load. > > This also had an effect on my analogy problem, but not completely... I = will > start a new thread for that... >=20 > If your latency drops under loads, it sounds as if your CPU is slowing > down when idle and taking a while to speed back up. Perhaps changing > the CPU governer to performance or user controlled and setting a fixed > CPU speed would keep the latency low all the time (although at the cost > of more power consumption). I had a similar problem where the latency behavior changed depending on the= CPU load on an Intel CPU (see " Problems with running Xenomai on Core i5" = thread of this list). It turned out to be a C1E "feature" that I could not = influence in the BIOS. But clearing the second bit of the MSR_IA32_POWER_CT= L register did help. I used the wrmsr command of the msr-tools package. -Tobias