On Fri, Jul 24, 2020 at 04:59:34PM +0200, Peter Zijlstra wrote: > On Fri, Jul 24, 2020 at 07:46:32AM -0700, Andi Kleen wrote: > > > Something that seems to 'work' is: > > > '{cycles,cpu/instructions,period=50000/}', so maybe you can make the > > > group modifier :S use any sampling event if there is one, and otherwise > > > designate the leader. > > > > > > Then you can write things like: > > > > > > '{slots, metric1, metric2, cpu/cycles,freq=50000/}:S' > > > > > > and then since cycles is specified as a sampling event, it will use > > > that. > > > > Okay possible, but it makes things more complicated > > for the user to understand and requires special documentation. > > Hopefully it's worth it the internal simplification. > > You already require special documentation for this metrics stuff. We > already need to state that SLOTS cannot be a sampling event, so you > already need to pay attention to this anyway. > > A shortcut could be a :s event modifier, then you can write: > > '{slots, metric1, metric2, cycles:s}:S' > > and have the tool select the :s tagged one.
Having slots as leader also would allow doing something like FORMAT_METRIC, where we return sibling/leader in some fashion. That also makes sense for instructions, because, IIRC, instructions/slots is the better IPC. And we should probably consider FORMAT_RESET.