A friend pointed this out:

http://www.brendangregg.com/linuxperf.html

Observability, methodologies, benchmarking, profiling, etc, for performance
tuning, which is a subject few may find useful, but I thought I would share it.
There are some youtube videos of his talks.

(The guy works at Netflix, so he must have some aim to covering performance
issues on massive content-distribution, etc, which some here may find useful.)