Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> writes: > Hi Alex, Hi Mathieu, > On Tue, 3 Jul 2018 at 04:03, Alexander Shishkin > <alexander.shishkin@xxxxxxxxxxxxxxx> wrote: >> >> On Mon, Jul 02, 2018 at 04:33:29PM -0600, Mathieu Poirier wrote: >> > This patch follows what has been done for filters by adding an ioctl() >> > option to communicate to the kernel arbitrary PMU specific configuration >> > that don't fit in the conventional struct perf_event_attr to the kernel. >> >> Ok, so what *is* the PMU specific configuration that doesn't fit in the >> attribute and needs to be re-configured by the driver using the generation >> tracking? >> > > In this patchset I'm am after the specification of sink information > for each event, i.e what sink a CPU is supposed to use for the > session. I simply don't see putting something that PMU specific in > the generic perf_event_attr structure. I also intend to use the same > ioctl mechanism to communicate complex tracer configuration for > sequencers, counters and input events. I don't see a nice way of > doing that from the perf_event_attr, and that is even without thinking > about the different flavours of tracers out there, all with their own > features. Yes, the sequencers and counters seem tricky. Here's a wild idea: can the sequencer/counter configuration be expressed as an eBPF program? Or, can an eBPF program be used to program those? > I've looked around and the only clean way I found to support this is > via an ioctl(). That way each tracer can easily identify the sink it > should be using without smearing the perf_event_attr structure. I > would be happy to explore a different avenue should you think of > something. Yes, I also have something similar on my todo list and I was previously thinking along the lines of pipe()/splice(). As in, you take the AUX event file descriptor and feed it to the sink, at which point the trace path is configured. I need to dig up the notes that I made back in the day to continue this conversation in more concrete terms. Regards, -- Alex -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
