How to Utilize 'cpufreq-aperf' for Monitoring CPU Frequency (with examples)

The cpufreq-aperf command is a powerful tool designed to calculate the average CPU frequency over a specified time period. This is particularly useful for system administrators and performance analysts seeking to monitor and analyze CPU frequency behavior under various workloads. The command requires root privileges due to the need to access low-level system information. By using cpufreq-aperf, users can gain insights into how efficiently the CPU is operating in terms of frequency without altering any settings. Detailed insights on how this valuable command can be employed across different scenarios are elaborated below.

Use case 1: Start calculating, defaulting to all CPU cores and 1 second refresh interval

Code:

sudo cpufreq-aperf

Motivation:

This default command setup is useful for users who want a quick start to monitor their CPU frequency without delving into any custom settings. By employing this, you get instantaneous feedback on how your CPU cores are performing in terms of frequency averages every second, making it ideal for real-time monitoring during typical system use or stress testing.

Explanation:

• sudo: Running with root privileges is mandatory because the command requires access to system-level information.
• cpufreq-aperf: Executes the program which calculates CPU frequencies. By default, it targets all available CPU cores and refreshes the average frequency calculation every second.

Example output:

CPU Frequency (Hz):
CPU 0: 3200000000
CPU 1: 3150000000
CPU 2: 3180000000
CPU 3: 3170000000

Use case 2: Start calculating for CPU 1 only

Code:

sudo cpufreq-aperf -c 1

Motivation:

In scenarios where a specific CPU core’s performance is of interest—such as debugging issues related to core-specific tasks or analyzing core pinning effects in multi-threaded applications—this command allows focused monitoring. It helps users isolate CPU core performance for targeted troubleshooting or performance validation.

Explanation:

• -c 1: The -c argument specifies a particular CPU core (in this case, CPU 1) for which to track the average frequency. This is helpful for investigations focused on a single core among many.

Example output:

CPU 1 Frequency (Hz):
3250000000

Use case 3: Start calculating with a 3 second refresh interval for all CPU cores

Code:

sudo cpufreq-aperf -i 3

Motivation:

When looking for a broader overview of CPU behavior over a longer timeframe, adjusting the refresh interval can provide more meaningful insights. A 3-second interval reduces CPU load generated by the monitoring itself and smoothens the data curve, better reflecting sustained performance levels rather than transient spikes or dips.

Explanation:

• -i 3: With this argument, the refresh interval is set to 3 seconds, allowing users to observe average frequencies over slightly longer periods, which might match better with certain monitoring needs.

Example output:

CPU Frequency (Hz) over 3 seconds:
CPU 0: 3195000000
CPU 1: 3175000000
CPU 2: 3185000000
CPU 3: 3165000000

Use case 4: Calculate only once

Code:

sudo cpufreq-aperf -o

Motivation:

There are instances when users require a quick snapshot of CPU performance without continuous monitoring. For example, capturing a one-time frequency reading might be apt during a specific event or while running a benchmark at a particular moment. This option provides that single, precise capture of CPU activity.

Explanation:

• -o: This argument instructs cpufreq-aperf to perform a single calculation and terminate, rather than continuously refreshing the output. It’s a simple way to get a one-time insight into the frequency states of your CPUs.

Example output:

CPU Frequency Snapshot (Hz):
CPU 0: 3202000000
CPU 1: 3187000000
CPU 2: 3198000000
CPU 3: 3169000000

Conclusion:

The cpufreq-aperf command is a versatile tool for monitoring CPU frequencies, offering users flexibility to tailor the observation scope to suit varied monitoring needs. Whether you require real-time insights, core-specific data, longer interval averages, or one-time snapshots, cpufreq-aperf accommodates with ease. Understanding how to apply these different use cases effectively can greatly enhance system diagnostics and performance evaluations.