Linux perf events: cpu-clock and task-clock - what is the difference

Question

Linux perf tools (some time ago named perf_events) has several builtin universal software events. Two most basic of them are: task-clock a

Answer 1

According to this message, they measure the same thing.

They just differ in when they sample.

cpu-clock is wall-clock based -- so samples are taken at regular intervals relative to walltime. I believe that task-clock is relative to the task run time. So, samples are taken at regular intervals relative to the process' runtime.

When I run it on my multi-threaded app, it indeed shows nearly identical values.