[$] User events — but not quite yet

The ftrace and perf subsystems provide visibility into the workings of thekernel; by activating existing tracepoints, interested developers can seewhat is happening at specific points in the code. As much as kerneldevelopers may resist the notion, though, not all events of interest on asystem happen within the kernel. Administrators will often want to lookinside user-space processes as well; they would be even happier with amechanism that allows the simultaneous tracing of events in both the kerneland user space. The user-eventssubsystem, developed by Beau Belgrave and addedduring the 5.18 merge window, promises that capability, but users will almost certainly have to waitanother cycle to gain access to it.