Popcorn Linux: enabling efficient inter-core communication in a Linux-based multikernel operating system

Abstract

As manufacturers introduce new machines with more cores, more NUMA-like architectures, and more tightly integrated heterogeneous processors, the traditional abstraction of a monolithic OS running on a SMP system is encountering new challenges. One proposed path forward is the multikernel operating system. Previous efforts have shown promising results both in scalability and in support for heterogeneity. However, one effort\'s source code is not freely available (FOS), and the other effort is not self-hosting and does not support a majority of existing applications (Barrelfish).

In this thesis, we present Popcorn, a Linux-based multikernel operating system. While Popcorn was a group effort, the boot layer code and the memory partitioning code are the author\'s work, and we present them in detail here. To our knowledge, we are the first to support multiple instances of the Linux kernel on a 64-bit x86 machine and to support more than 4 kernels running simultaneously.

We demonstrate that existing subsystems within Linux can be leveraged to meet the design goals of a multikernel OS. Taking this approach, we developed a fast inter-kernel network driver and messaging layer. We demonstrate that the network driver can share a 1 Gbit/s link without degraded performance and that in combination with guest kernels, it meets or exceeds the performance of SMP Linux with an event-based web server. We evaluate the messaging layer with microbenchmarks and conclude that it performs well given the limitations of current x86-64 hardware. Finally, we use the messaging layer to provide live process migration between cores.