In this article we described the CPUFreq feature of the Linux Kernel and demonstrated how to switch between CPU scaling governor modes without rebooting the host. # cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor Switch to the ‘performance’ mode: $ echo "performance" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governorĮnsure the CPU scaling governor is in performance mode by checking the following here you will see the setting from each processor (vcpu). Put your CPU’s in ‘performance’ modeĬheck the current mode: # cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor You can read more details about the CPUFreq Linux feature and configuration options in the Kernel Documentation. The request is made once at that time the governor for the policy is set to powersave and whenever the scaling_max_freq or scaling_min_freq policy limits change after that. When attached to a policy object, this governor causes the lowest frequency, within the scaling_min_freq policy limit, to be requested for that policy. The request is made once at that time the governor for the policy is set to performance and whenever the scaling_max_freq or scaling_min_freq policy limits change after that. When attached to a policy object, this governor causes the highest frequency, within the scaling_max_freq policy limit, to be requested for that policy. The definition for ‘powersave’ and ‘performance’ scaling governors are: By default, most Linux distributions place the system into a ‘powersave’ mode. For benchmarking, we usually want maximum performance and power. The Linux kernel supports CPU performance scaling by means of the CPUFreq (CPU Frequency scaling) subsystem that consists of three layers of code: the core, scaling governors and scaling drivers. Therefore there is a natural trade-off between the CPU capacity (the number of instructions that can be executed over a unit of time) and the power drawn by the CPU. As a rule, the higher the clock frequency and the higher the voltage, the more instructions can be retired by the CPU over a unit of time, but also the higher the clock frequency and the higher the voltage, the more energy is consumed over a unit of time (or the more power is drawn) by the CPU in the given P-state. The majority of modern processors are capable of operating in a number of different clock frequency and voltage configurations, often referred to as Operating Performance Points or P-states (in ACPI terminology).
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