• Tvrtko Ursulin's avatar
    drm/i915/pmu: Expose a PMU interface for perf queries · b46a33e2
    Tvrtko Ursulin authored
    From: Chris Wilson <chris@chris-wilson.co.uk>
    From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
    From: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
    
    The first goal is to be able to measure GPU (and invidual ring) busyness
    without having to poll registers from userspace. (Which not only incurs
    holding the forcewake lock indefinitely, perturbing the system, but also
    runs the risk of hanging the machine.) As an alternative we can use the
    perf event counter interface to sample the ring registers periodically
    and send those results to userspace.
    
    Functionality we are exporting to userspace is via the existing perf PMU
    API and can be exercised via the existing tools. For example:
    
      perf stat -a -e i915/rcs0-busy/ -I 1000
    
    Will print the render engine busynnes once per second. All the performance
    counters can be enumerated (perf list) and have their unit of measure
    correctly reported in sysfs.
    
    v1-v2 (Chris Wilson):
    
    v2: Use a common timer for the ring sampling.
    
    v3: (Tvrtko Ursulin)
     * Decouple uAPI from i915 engine ids.
     * Complete uAPI defines.
     * Refactor some code to helpers for clarity.
     * Skip sampling disabled engines.
     * Expose counters in sysfs.
     * Pass in fake regs to avoid null ptr deref in perf core.
     * Convert to class/instance uAPI.
     * Use shared driver code for rc6 residency, power and frequency.
    
    v4: (Dmitry Rogozhkin)
     * Register PMU with .task_ctx_nr=perf_invalid_context
     * Expose cpumask for the PMU with the single CPU in the mask
     * Properly support pmu->stop(): it should call pmu->read()
     * Properly support pmu->del(): it should call stop(event, PERF_EF_UPDATE)
     * Introduce refcounting of event subscriptions.
     * Make pmu.busy_stats a refcounter to avoid busy stats going away
       with some deleted event.
     * Expose cpumask for i915 PMU to avoid multiple events creation of
       the same type followed by counter aggregation by perf-stat.
     * Track CPUs getting online/offline to migrate perf context. If (likely)
       cpumask will initially set CPU0, CONFIG_BOOTPARAM_HOTPLUG_CPU0 will be
       needed to see effect of CPU status tracking.
     * End result is that only global events are supported and perf stat
       works correctly.
     * Deny perf driver level sampling - it is prohibited for uncore PMU.
    
    v5: (Tvrtko Ursulin)
    
     * Don't hardcode number of engine samplers.
     * Rewrite event ref-counting for correctness and simplicity.
     * Store initial counter value when starting already enabled events
       to correctly report values to all listeners.
     * Fix RC6 residency readout.
     * Comments, GPL header.
    
    v6:
     * Add missing entry to v4 changelog.
     * Fix accounting in CPU hotplug case by copying the approach from
       arch/x86/events/intel/cstate.c. (Dmitry Rogozhkin)
    
    v7:
     * Log failure message only on failure.
     * Remove CPU hotplug notification state on unregister.
    
    v8:
     * Fix error unwind on failed registration.
     * Checkpatch cleanup.
    
    v9:
     * Drop the energy metric, it is available via intel_rapl_perf.
       (Ville Syrjälä)
     * Use HAS_RC6(p). (Chris Wilson)
     * Handle unsupported non-engine events. (Dmitry Rogozhkin)
     * Rebase for intel_rc6_residency_ns needing caller managed
       runtime pm.
     * Drop HAS_RC6 checks from the read callback since creating those
       events will be rejected at init time already.
     * Add counter units to sysfs so perf stat output is nicer.
     * Cleanup the attribute tables for brevity and readability.
    
    v10:
     * Fixed queued accounting.
    
    v11:
     * Move intel_engine_lookup_user to intel_engine_cs.c
     * Commit update. (Joonas Lahtinen)
    
    v12:
     * More accurate sampling. (Chris Wilson)
     * Store and report frequency in MHz for better usability from
       perf stat.
     * Removed metrics: queued, interrupts, rc6 counters.
     * Sample engine busyness based on seqno difference only
       for less MMIO (and forcewake) on all platforms. (Chris Wilson)
    
    v13:
     * Comment spelling, use mul_u32_u32 to work around potential GCC
       issue and somne code alignment changes. (Chris Wilson)
    
    v14:
     * Rebase.
    
    v15:
     * Rebase for RPS refactoring.
    
    v16:
     * Use the dynamic slot in the CPU hotplug state machine so that we are
       free to setup our state as multi-instance. Previously we were re-using
       the CPUHP_AP_PERF_X86_UNCORE_ONLINE slot which is neither used as
       multi-instance, nor owned by our driver to start with.
     * Register the CPU hotplug handlers after the PMU, otherwise the callback
       will get called before the PMU is initialized which can end up in
       perf_pmu_migrate_context with an un-initialized base.
     * Added workaround for a probable bug in cpuhp core.
    
    v17:
     * Remove workaround for the cpuhp bug.
    
    v18:
     * Rebase for drm_i915_gem_engine_class getting upstream before us.
    
    v19:
     * Rebase. (trivial)
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    Signed-off-by: default avatarDmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
    Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
    Cc: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20171121181852.16128-2-tvrtko.ursulin@linux.intel.com
    b46a33e2
intel_ringbuffer.h 30.6 KB