Isolation Mechanisms for Cloud Workloads: Rethinking Containers with Microkernels

What is it about?

In cloud computing, workloads from different tenants must be isolated to ensure security, performance, and resource efficiency. Isolation mechanisms such as processes, containers, and virtual machines (VMs) play a crucial role in achieving this. Processes are the lightest and most resource-efficient, but they offer limited isolation guarantees. On the other hand, VMs provide robust isolation but come with higher overhead. Containers bridge this gap, offering a lightweight isolation mechanism with stronger guarantees than processes but less overhead than VMs. Function-as-a-Service (FaaS) workloads, a growing trend in cloud computing, often involve many short-lived function invocations. These workloads require an isolation mechanism that is both lightweight for rapid startups and strong enough to ensure tenant isolation. Linux-based containers are widely used for this purpose. However, these containers rely on mechanisms that were retroactively added to the Linux kernel, such as seccomp-bpf for system call filtering and namespaces for resource isolation. Since the Linux kernel is monolithic, these additions increase its complexity and expand its attack surface. We argue that a microkernel-based operating system architecture offers a compelling alternative for building secure and high-performing containers. Unlike monolithic systems, microkernels implement core services as separately isolated components accessed through a capability-based model. Capabilities serve as a robust access control mechanism, inherently enabling features like system call filtering and resource visibility restriction that are essential for container isolation. Our preliminary work demonstrates that microkernel-based containers can achieve comparable or even superior performance in microbenchmarks. These results highlight the potential for microkernel-based systems to support lightweight and secure containerized FaaS workloads. We are actively working towards a complete prototype that can execute real-world FaaS workloads, aiming to combine the best of both worlds: strong isolation with minimal overhead.

Featured Image

Photo by Growtika on Unsplash

Photo by Growtika on Unsplash

Why is it important?

This topic is critical and timely because modern cloud computing increasingly relies on Function-as-a-Service (FaaS) workloads, which demand fast startup times, high scalability, and strong tenant isolation. Existing solutions like Linux containers, while widely adopted, face inherent limitations due to their reliance on retrofitted mechanisms within a monolithic kernel. These limitations increase complexity and security risks, making it difficult to meet the evolving needs of cloud-scale environments. Microkernel-based architectures offer an opportunity to rethink isolation mechanisms from the ground up. By providing lightweight and inherently secure building blocks, they address security challenges in ways that monolithic kernels cannot. The urgency of addressing these challenges is underscored by the growing reliance on cloud services for everything from enterprise applications to real-time data processing, where efficiency and security are critical to scalability and trust. As cloud workloads grow in complexity and volume, exploring such alternatives is not just relevant but necessary to ensure future-proof, efficient, and secure computing environments.

Perspectives