The man page for perf_event_open(2) says that recent kernels treat a 0 value for wakeup_events the same as 1, which I believe means it will notify after a single sample. However, strace on perf(1) shows that it uses wakeup_events=0, and it's definitely not waking up on every sample (it seems to be waking up every few seconds.) tools/perf/design.txt says "Normally a notification is generated for every page filled". Is the documentation wrong, or am I misunderstanding something? ~Theodore