Xen Developer & Design Virtual Summit 2020

Deterministic IRQ latency is a hard requirement for many embedded deployments. Even small spikes lead to failure. No matter the activity in other VMs, the latency-sensitive app has to continue unaffected.

Xen can fully dedicate physical CPUs to VMs to minimize latency and interference. However, real-time deadlines can still be missed due to the presence of a shared L2 cache across the ARM cores. One app on one CPU core can affect the performance of another app in a different VM by causing cache interference.

The solution is cache coloring. This presentation will introduce the new Xen feature to achieve deterministic latency on ARM systems. Cache coloring enables memory allocations with entirely dedicated cache line entries. The presentation will show how to configure a cache coloring Xen deployment and will demonstrate its benefits with detailed latency measurements and live demos.