User time is the amount of CPU time spent in user mode. It is aggregated across threads. If you have 8 threads running at 100% in user mode for 1 second, that g

User time is the amount of CPU time spent in user mode. It is aggregated across threads. If you have 8 threads running at 100% in user mode for 1 second, that gives you 8s of user time. Total CPU time in user mode will normally increase when you add more threads, unless you're getting perfect or better-than-perfect scaling.