[jerrinot]

Only for some clocks (CLOCK_MONOTONIC, etc) and some clock sources. For VIRT/SCHED, the vDSO shim still has to invoke the actual syscall. You can't avoid the kernel transition when you need per-thread accounting.

[touisteur]

Oh for some time after its introduction, CLOCK_MONOTONIC_RAW wasn't vDSO'd and it took some time and syscall profiling ('huh, why do I see these as syscalls in perf record -e syscalls' ...) to understand what was going on.

[higherhalf]

Thanks, I really should've looked deeper than that.

[jerrinot]

no problem at all, I was confused too when I saw the profile for the first time.