http://imil.net/blog/tags/powernow/ Recent content in PowerNow on iMil.net Hugo en-us Thu, 02 May 2013 09:49:49 +0000 http://imil.net/blog/posts/2013/cpu-dynamic-scaling-on-netbsd/ Thu, 02 May 2013 09:49:49 +0000 http://imil.net/blog/posts/2013/cpu-dynamic-scaling-on-netbsd/ <p>I know about <a href="http://wiki.netbsd.org/tutorials/cpu_frequency_scaling/">estd</a> for a while, that daemon &ldquo;dynamically sets the CPU-frequency on Enhanced SpeedStep, PowerNow, and APCI P-States-enabled CPUs depending on current cpu-utilization&rdquo; (manpage excerpt). Thing is, I&rsquo;ve never seen any CPU changing from its current speed while monitoring the <code>machdep.powernow.frequency.current</code> <em>sysctl</em>.</p> <p>In order to understand what was happening, I started <code>estd</code> with the <code>-o</code> flag, which outputs the CPU-frequencies as they are set. I then realized that the &ldquo;ligh watermark percentage&rdquo; and &ldquo;low watermark percentage&rdquo; default values were way too high (respectively 40 and 80) and were never reached, so the CPU speed was never changed.</p>