On Thu, 2012-08-16 at 19:45 +0200, Borislav Petkov wrote: > > off and on I get some free time to work on that, here's the latest > incarnation. It contains review feedback from the earlier round. > > Patch 1/4 adds a trace_add_file() interface which adds an additional > file to debugfs, in this case the "persistent" file which contains the > normal perf file descriptor sys_perf_event_open gives to the perf tool. > > IOW, one gets: > > /mnt/dbg/tracing/events/mce/mce_record/ > |-- enable > |-- filter > |-- format > |-- id > `-- persistent1 > > 0 directories, 5 files > > [ 1 is the CPU number so sticking all per-CPU descriptors in this > directory could get a little cluttered and ugly so I'll have to think > about that a bit more. ] > > 3/4 is the meat which adds <kernel/events/persistent.c> and 4/4 shows > how one can init a persistent event on a CPU. > > What remains is adding code which can enable events on boot from the > kernel cmdline and more testing. > > As always, comments and suggestions are appreciated.
Good progress there, there's still a few things though: - the point also raised by Steven, I'm pretty sure that the placing of the debugfs files unfortunate. I would much rather see something like /debug/perf/persistent/$foo, also dropping your perf_event_desc::dir_name. - I would make perf_add_persistent_on_cpu() static and create something like perf_add_persistent() which iterates all CPUs and creates: "%s-%04d", perf_event_desc::fname, cpu. This needs a little extra for cpu-hotplug, not sure what to do there. - related to the first point, by not tying them to actual events you can create a persistent 'event' that contains multiple events. Its quite possible to create multiple kernel events and use the equivalent of PERF_EVENT_IOC_SET_OUTPUT on them to the exposed FD. - It might be good to provide means of changing the persistent event's buffer size, or maybe even 'destroy' persistent buffers. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
