Edge workloads by their nature are resource-constrained, meaning they don’t have the luxury of the cloud to just scale up / add more instances to deal with any performance issues. Edge workloads have to work with the resources they have and try to schedule and share resources fairly and according to policy. This sounds like something that should “just” work in 2022, but in practice, a resource-hungry workload can end up stealing resources from other workloads in a multi-tenant environment. In most virtualization solutions there are controls that try to ensure there are software firewalls between workloads and this scenario does not happen, but most people at some point have experienced someone else’s database job that thrashes IO, or math-heavy FPU (floating-point unit) job that stresses the CPU, and your workload struggles to respond and takes on unacceptable latency.
Noisy Neighbor
This is what's known as the noisy neighbor effect, this is wherein a multi-tenant environment (especially virtualization) and other tenants can affect your workload. Almost any metric can be affected; CPU utilization, memory availability, and storage IO to name a few.
When this situation arises for edge workloads it can be very disruptive to workloads, where a majority are already latency-sensitive or real-time dependent. Latency can distort response times as well as cause issues or break the real-time guarantees that are needed for real-time operating systems and apps.
Performance Tuning
In virtual environments there are knobs admins can turn to tune a system and try to reduce these noisy effects, like CPU pinning, rebalancing workloads across infrastructure (if available), setting quota limits in the virtual machine manager, offloading network functions to newer network cards, and I’m sure there are many others you can think of but most of these reside at the software level and your mileage may vary with these settings.
Hardware-Based Isolation
With newer processors hitting the market in the last few years, there has been a multitude of new features that can tackle noisy neighbors at a much lower level, in the hardware.
Stay tuned for my next article where we dig into some of these features and see if they can help to combat noisy neighbors.
