This talk by Brendan Gregg is a fantastic introduction to the tools available in linux for performance instrumentation, monitoring, and debugging.

• perf-tools: https://github.com/brendangregg/perf-tools
• ebpf: https://ebpf.io/
• strace: https://man7.org/linux/man-pages/man1/strace.1.html
• valgrind: https://valgrind.org/
• ftrace: https://lwn.net/Articles/608497/
• uprobes: https://www.brendangregg.com/blog/2015-06-28/linux-ftrace-uprobe.html
• uptime
• dmesg | tail
• iostat ­xz 1
• sar -n DEV 1
• sar -n TCP,ETCP 1