Hi, I've been working on adding support for heterogeneous pmus (as would be found in big.LITTLE systems) to the arm perf backend, and in the process of doing so I've noticed a few issues in the core perf code that would be nice to have fixed up. The heterogeneous pmu support is not quite ready, but the core changes are independent, so I'm posting them today.
The first three patches fix up some basic issues which are relevant regardless of whether you wish to deal with heterogeneous pmus, though patch two also fixes a potential bug when perf_event_contexts are shared by multiple pmus. The remaining four patches attempt to fix some inconsistencies in perf core with regard to multiple pmus sharing perf_event_contexts, taken to the extreme of removing perf_event_context::pmu. These result in an odd edge-case with a shared hrtimer_interval_ms being exported per-pmu, and also highlight how odd it is to have a group of events from multiple pmus (given that should mean the group can never be scheduled). Based on commit 443772776c69 (perf: Disable all pmus on unthrottling and rescheduling) I believe that pmus sharing a context is the expected behaviour, but given the edge cases this series highlights I think it would make more sense to disallow context sharing and allocate a unique context per-pmu instead (which would also make ctx->pmu sane again). I'm happy to rework the series to that effect if people agree with the approach. Patch 4 of this series (be less pessimistic when scheduling events) can be improved with some standardisation of error codes returned by pmu::add, but for the moment I've kept myself away from the architecture backends. The current heterogeneous pmu series based atop of this can be found on my linux-arm git repo [1]. Patches are based on v3.14-rc1. Thanks, Mark. [1] git://linux-arm.org/linux-mr.git devel/perf/multi-pmu Mark Rutland (7): perf: fix prototype of find_pmu_context perf: remove redundant pmu assignment perf: kill perf_event_context_type perf: be less pessimistic when scheduling events perf: kill pmu::hrtimer_interval_ms perf: Centralise context pmu disabling perf: kill perf_event_context::pmu include/linux/perf_event.h | 10 +-- kernel/events/core.c | 162 +++++++++++++++++++++++---------------------- 2 files changed, 85 insertions(+), 87 deletions(-) -- 1.8.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
