Accelerating Datacenter Energy Efficiency by Leveraging FreeBSD as Your Server OS

Datacenters are large facilities that house computer systems and other electronic equipment that are used to store, process, and transmit data. These facilities are critical components of the modern digital economy, but they also consume vast amounts of energy. In fact, datacenters are estimated to account for around 1% of global electricity consumption, and that figure is projected to grow as digital technologies continue to expand.

Dealing with a New Era of Energy
Efficiency

Given the significant energy consumption of datacenters, there is a growing recognition that these facilities need to be designed and operated with energy efficiency in mind. This is where datacenter energy goals come into play. These goals are typically established by datacenter operators or by governments and industry groups that seek to encourage energy-efficient practices in the datacenter industry.

Can Operating Systems Really Play a Role in Limiting the Energy Consumption?

The simple answer is: Yes, operating systems can play a significant role in datacenter energy efficiency. The operating system is the software that manages the resources and services of a computer system, and it can be optimized to reduce energy consumption in several ways:

1. Power management: Most modern operating systems include power management features that allow them to adjust the power consumption of the system based on its workload. This can include reducing the clock speed of the CPU when idle, or overclocking a single core to complete a task more quickly and return to a low energy state, as well as shutting down unused peripherals, and adjusting the transmit power of network devices.
2. Virtualization: Virtualization allows multiple operating systems to run on the same physical hardware, which can help reduce energy consumption by increasing server
   utilization rates.
3. Resource allocation: Operating systems can also optimize the allocation of
   resources such as CPU, memory, and storage to reduce energy consumption. For example, by prioritizing applications and services based on their energy usage, the operating system can ensure that the most energy-efficient applications are given priority access to resources.
4. Performance optimization: By optimizing the performance of applications and services, operating systems can reduce the overall workload of the system, which can in turn reduce energy consumption.

Make Room, FreeBSD is Here to
Help

Unless you’re new to FreeBSD, you’re already aware that FreeBSD is an open source operating system that is currently used both as an underlaying platform for different system or as a server OS. 

So how does FreeBSD tackle the energy conversation? One way that it can help to reach datacenter energy goals is by providing a stable and efficient platform for running servers and other datacenter infrastructure. Additionally, because it is open source, it allows for customization and optimization of the operating system to better fit the specific needs of a datacenter and potentially reduce energy consumption. Additionally, the power management feature in FreeBSD such as CPU frequency scaling and powered can help to reduce energy consumption.

Another way that FreeBSD can help to reduce energy consumption in datacenters is through its efficient memory management. FreeBSD uses advanced memory management techniques such as transparent superpages, page laundering, and the ability to move inactive pages to disk, which can improve the performance of the more active workload and thus reduce energy consumption.

A Deep(er) Dive Into FreeBSD Memory
Management

FreeBSD uses several advanced memory management techniques to improve efficiency and reduce energy consumption.  The first of these techniques, transparent superpages, allows the OS to group a range of 4 KB memory pages into a single larger mapping of 2 MB of even larger sizes supported by the CPU architecture. This 512-to-1 mapping reduces complexity and improves performance by reducing the number of expensive translation lookaside buffer lookups. Improving the performance of the workload correspondingly reduces the amount of energy required.

Another technique used by FreeBSD is the ability to move inactive pages to disk, also known as "swapping" or "paging". This allows the operating system to offload infrequently used pages of memory to disk, freeing up space in physical memory for active pages. This technique makes more memory available for active tasks, which allows them to complete more quickly, and can help to reduce energy consumption.

In addition, a technique called "memory ballooning" can be used to dynamically adjust the amount of memory allocated to virtual machines. This allows the host to present the guest operating system with a larger amount of memory, then dynamically adjust how much of that memory is
allocated to each virtual machine based on its current usage, which can help to reduce energy consumption by allocating additional memory to the busiest virtual machines.

Overall, FreeBSD uses advanced memory management techniques such as transparent superpages, swapping, and memory ballooning to improve efficiency and reduce energy consumption.

Optimizing CPU Usage for More Energy
Efficiency

CPU frequency scaling is a technique used by the operating system to adjust the clock speed of the processors based on workload. In FreeBSD, this feature is provided by the CPU Frequency Control (CFC) subsystem which is based on the Advanced Configuration and Power Interface (ACPI) specification and the CPU frequency driver, cpufreq(4).

When the system is idle, the CFC subsystem can lower the clock speed of the processors, which reduces the amount of energy consumed by the processors. This can help to reduce overall energy consumption in the datacenter. As the workload increases, the CFC subsystem can increase the clock speed of the processors to handle the increased workload, which ensures that the system remains responsive.

Additionally, it also has the ability to set the maximum and minimum CPU frequency, this allows the administrator to set the maximum frequency to the lowest possible value that will meet the demands of the running workload, and in this way, reduces the energy consumption of the processors.

The FreeBSD cpufreq(4) driver also makes use of hardware specific functionality, including Intel Enhanced Speedstep and SpeedShift, and AMD’s Cool’n’Quiet2. In addition to allowing the OS to lower the clock speed to reduce power consumption, these drivers also allow the operating system to enable turbo boost features to increase the clock speed beyond the normal maximum for short periods of time, temporarily increasing power consumption, but allowing the system to complete the work and return to a lower power state sooner, reducing overall power consumption.

CPU frequency scaling in FreeBSD can help to reduce energy consumption by adjusting the clock speed of the processors based on workload, and by allowing the administrator to set the maximum frequency to the lowest possible value that will meet the demands of the running workload. This can help to reduce overall energy consumption in the datacenter.

Conclusions

While it might not be the largest step to starting to tackle datacenter energy consumption, tweaking from the OS side is definitely an easy-to-implement step on that journey. Hardware replacements take time, extensive overhauls of cooling and other physical plant take even longer to plan and deploy. Doing a minimum optimization in an operating system such as FreeBSD, where you have all the options at your disposal can already make a dent in the consumption level. Optimizing your systems and workloads to be as optimized as possible makes the biggest impact on energy consumption. Consider a Klara Performance Audit to make sure you are infrastructure is working at peak efficiency.