Messages in this thread | | | From | Alexander Shishkin <> | Subject | Re: [PATCH 5/6] perf/core: Use ioctl to communicate driver configuration to kernel | Date | Wed, 04 Jul 2018 13:51:22 +0300 |
| |
Mathieu Poirier <mathieu.poirier@linaro.org> writes:
> Hi Alex,
Hi Mathieu,
> On Tue, 3 Jul 2018 at 04:03, Alexander Shishkin > <alexander.shishkin@linux.intel.com> 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
| |