Power efficiency is now a major feature for contemporary embedded systems. Whether it is industrial controllers or edge platforms, embedded Linux applications are supposed to perform well without wasting energy. Inefficient power management results in early device failure, high temperature stress, and the rise of the cost of operation. Therefore, it is common that a lot of teams seeking help with power efficient systems resort to an expert in embedded linux development services.
The power saving is not just about switching one setting or using a particular feature. It can be a mix of software decisions, kernel configuration, hardware interaction, and runtime behavior. If done right, the power savings may be quite substantial without the loss of features.
Understanding where power is consumed
Even if applications are not actively being used (being idle), they still consume power by various background processes such as services that run in the background (background service), unnecessary drivers, frequent wakeups (going into and waking out of sleep states), and poor CPU scheduling. If power loss can be detected at an early stage, then better optimization is possible.
- Power consumption will typically include three main categories:
- CPU and clock activity
- Peripheral usage
- Memory access patterns
The sources of power loss through background processes (daemons) are directly correlated to CPU utilization, as CPU utilization affects all layers in the system. Therefore, optimizing all three layers will significantly reduce power consumption.
Kernel configuration matters
The Linux kernel has a significant impact on power consumption. A generic kernel generally contains features and drivers that might not be necessary for a specific device. These extraneous components, even if they are not used, still consume power.
Custom kernel configuration can be beneficial by:
- turning off unused drivers and modules
- allowing CPU frequency scaling
- supporting deep sleep states
- minimizing interrupt overhead
A slim kernel makes it possible for the hardware to maintain low power modes for a longer duration.
Managing CPU frequency and idle states
Dynamic frequency scaling enables processors to adapt processor speed according to the amount of work being performed. Keeping the CPU running at a constant maximum speed is a waste of energy, so various Linux governors enable operating systems to dynamically change CPU frequency with workload in order to optimise performance and power usage.
Similar to dynamic frequency scaling is idle state management. A computer or device that can be put into a deeper sleep state while it is not being used will consume far less power. Properly configuring CPUs to enter these possible sleepy states will ensure that there is no unnecessary wake-up during idleness.
Optimizing application behavior
Applications are a common source of power wastage due to poor design. Continuous loops, too many logs, and very frequent polling are the problems that keep the system active even when there is no real work to be done.
More effective software design comprises:
- using event driven programming rather than polling
- grouping the operations so as to reduce wakeups
- avoiding unnecessary accesses to the disk and network
- cutting down on the unwanted debug output
Even minor alterations to the app logic can turn into big energy savings.
Device driver and peripheral control
Power is consumed by peripherals even if they are not in use. The display, communication module, sensor, and storage devices are all considered peripherals, and they require careful monitoring. The following methods create effective power control of unused peripherals:
- Turn off unused devices
- Suspend devices during idle time
- Use runtime power management features
- Synchronize device activity to match the system state
Device drivers that support powering down devices will help greatly reduce the total power consumed by a device.
Monitoring and profiling power usage
Optimizing your device’s power consumption without measurements/quantity is just educated guessing. While profiling tools are used to determine what is preventing a device from entering into sleep mode and where power is being wasted on a device.
- Tracking CPU wakeups
- Monitoring process activity.
- The charge of any devices that are connected to the system.
- Analyzing the amount of time the system is in sleep mode and how it resumes when it goes into sleep mode.
- Using data-driven methods allows for accurate and predictable results.
Designing for power from the start
It is easier to improve power efficiency early in the development phase. An attempt to retrofit a power optimization at a later point will usually result in compromises. When the hardware selection, the operating system (OS) configuration and the application design are aligned with the power optimization goals, then the resulting power savings will be integrated into the overall architecture of the system, instead of being a post-build add-on.
Using this approach helps to increase:
- Battery life
- Thermal stability
- System reliability
- Long-term maintenance
Reducing the power consumption of embedded Linux applications requires that the kernel, drivers, and application layers work together to make coordinated decisions. If power management is included in the design process, the resulting systems will be more reliable, efficient, and scalable. At Sunstream, through our embedded software development services and PCB layout services for microcontrollers, we deploy a profound knowledge to help companies engineer their power optimized embedded solutions that not only achieve performance goals but also prolong the lifespan of the devices.
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