ppc64 scheduling issue with pinned and exclude_hv

[Vince Weaver]

Will Cohen reports (on 7 June 2017):

Michael Petlan and I have been noticing some problems with the check_schedulability function in the perf_event component failing on some ppc64 machines when the nmi_watchdog timer was enabled with ("echo 1 > /proc/sys/kernel/nmi_watchdog"). It seems this problem is due to constaints on the events that can be scheduled together. In particular the exclude_hv and pinned attribute are both set in the performance events in most cases for papi. However, if the watchdog is set to use the performance monitoring unit and it has the exclude_hv attribute cleared and the pinned attribute set. It appears on the ppc64 hardware that all the events being monitored at the same time need to have the same settings for exclude_hv, exclude_kernel, and exclude_user. The result with the trying to have these conflicting perf events attributes is that the read in the check_scedulabilty return 0 and a PAPI_ECNFLT is returned.