Re: [PATCH v2] drm/i915/pmu: Reconstruct active state on starting busy-stats

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 10/01/2018 16:11, Chris Wilson wrote:
> We have a hole in our busy-stat accounting if the pmu is enabled during
> a long running batch, the pmu will not start accumulating busy-time
> until the next context switch. This then fails tests that are only
> sampling a single batch.
> 
> v2: Count each active port just once (context in/out events are only on
> the first and last assigment to a port).
> 
> Testcase: igt/perf_pmu/busy-start
> Testcase: igt/perf_pmu/busy-double-start
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/intel_engine_cs.c  | 10 +++++++++-
>   drivers/gpu/drm/i915/intel_ringbuffer.h |  2 +-
>   2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 6bb51a502b8b..3a11602e60c7 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -1951,8 +1951,16 @@ int intel_enable_engine_stats(struct intel_engine_cs *engine)
>   	spin_lock_irqsave(&engine->stats.lock, flags);
>   	if (engine->stats.enabled == ~0)
>   		goto busy;
> -	if (engine->stats.enabled++ == 0)
> +	if (engine->stats.enabled++ == 0) {
>   		engine->stats.enabled_at = ktime_get();
> +
> +		/* XXX submission method oblivious? */
> +		engine->stats.active =
> +			port_isset(&engine->execlists.port[1]) +
> +			port_isset(&engine->execlists.port[0]);
> +		if (engine->stats.active)
> +			engine->stats.start = engine->stats.enabled_at;
> +	}
>   	spin_unlock_irqrestore(&engine->stats.lock, flags);
>   
>   	return 0;
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index c5ff203e42d6..37cf665692e5 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -225,7 +225,7 @@ struct intel_engine_execlists {
>   #define port_pack(rq, count) ptr_pack_bits(rq, count, EXECLIST_COUNT_BITS)
>   #define port_unpack(p, count) ptr_unpack_bits((p)->request_count, count, EXECLIST_COUNT_BITS)
>   #define port_set(p, packed) ((p)->request_count = (packed))
> -#define port_isset(p) ((p)->request_count)
> +#define port_isset(p) (((p)->request_count) != NULL)
>   #define port_index(p, execlists) ((p) - (execlists)->port)
>   
>   		/**
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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