CPU Thermal Throttling or Auto-Idling

Problem

Current-generation CPUs monitor themselves for thermal overheat. If the CPU is running on the edge of its manufacturer's specified thermal tolerance, the CPU will reduce its clock rate in order to keep from overheating. This reduces overall system performance, including ioDrive performance.

Some systems have a CPU idle detector installed as well. This decreases the clock rate of the CPU under low load in order to conserve power, but it also decreases overall system performance.

Solution

To detect a CPU running at a slower rate, inspect the contents of /proc/cpuinfo (in the Linux kernel) for discrepancies between the speed reported by the model and the current running speed. This must be done for each of the CPUs included in the listing.

Below is sample output of a system that has been throttled from 2.66 GHz to 1 GHz.

Figure 16 – CPU throttling