Tracing System CPU on Debian Stretch

What this post added

This post details a deep dive into system-level performance issues encountered during an upgrade from Debian Jessie to Debian Stretch, specifically focusing on increased system CPU usage and RCU stalls on Kafka nodes. It highlights the use of `perf` for profiling and `dmesg` for identifying kernel-level issues like memory allocation stalls and dropped kernel messages, ultimately leading to the identification of a regression in the Linux kernel between Debian Jessie and Stretch as the root cause.