[Intel-gfx] [PATCH 7/7] drm/i915: Engine queues query

[Lionel Landwerlin]

On 19/03/18 18:16, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>
> As well as exposing active requests on engines via PMU, we can also export
> the current raw values (as tracked by i915 command submission) via a
> dedicated query.
>
> This is to satisfy customers who have userspace load balancing solutions
> implemented on top of their custom kernel patches.
>
> Userspace is now able to include DRM_I915_QUERY_ENGINE_QUEUES in their
> query list, pointing to initialized struct drm_i915_query_engine_queues
> entry. Fields describing engine class and instance userspace would like to
> know about need to be filled in, and i915 will fill in the rest.
>
> Multiple engines can be queried in one go by having multiple queries in
> the query list.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_query.c | 43 +++++++++++++++++++++++++++++++++++++++
>   include/uapi/drm/i915_drm.h       | 26 +++++++++++++++++++++++
>   2 files changed, 69 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
> index 3ace929dd90f..b3bc69e8deb7 100644
> --- a/drivers/gpu/drm/i915/i915_query.c
> +++ b/drivers/gpu/drm/i915/i915_query.c
> @@ -82,9 +82,52 @@ static int query_topology_info(struct drm_i915_private *dev_priv,
>   	return total_length;
>   }
>   
> +static int
> +query_engine_queues(struct drm_i915_private *i915,
> +		    struct drm_i915_query_item *query_item)
> +{
> +	struct drm_i915_query_engine_queues __user *query_ptr =
> +				u64_to_user_ptr(query_item->data_ptr);
> +	struct drm_i915_query_engine_queues query;
> +	struct intel_engine_cs *engine;
> +	const int len = sizeof(query);
> +	unsigned int i;
> +
> +	if (query_item->flags)
> +		return -EINVAL;
> +
> +	if (!query_item->length)
> +		return len;
> +	else if (query_item->length < len)
> +		return -ENOSPC;

topology returns EINVAL in that case. I think ENOSPC makes more sense, 
do we need to change topology?

> +
> +	if (copy_from_user(&query, query_ptr, len))
> +		return -EFAULT;
> +
> +	for (i = 0; i < ARRAY_SIZE(query.rsvd); i++) {
> +		if (query.rsvd[i])
> +			return -EINVAL;
> +	}
> +
> +	engine = intel_engine_lookup_user(i915, query.class, query.instance);
> +	if (!engine)
> +		return -ENOENT;
> +
> +	query.queued = atomic_read(&engine->request_stats.queued);
> +	query.runnable = engine->request_stats.runnable;
> +	query.running = intel_engine_last_submit(engine) -
> +			intel_engine_get_seqno(engine);
> +
> +	if (copy_to_user(query_ptr, &query, len))
> +		return -EFAULT;
> +
> +	return len;
> +}
> +
>   static int (* const i915_query_funcs[])(struct drm_i915_private *dev_priv,
>   					struct drm_i915_query_item *query_item) = {
>   	query_topology_info,
> +	query_engine_queues,
>   };
>   
>   int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 9a00c30e4071..064c3d620286 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1637,6 +1637,7 @@ struct drm_i915_perf_oa_config {
>   struct drm_i915_query_item {
>   	__u64 query_id;
>   #define DRM_I915_QUERY_TOPOLOGY_INFO    1
> +#define DRM_I915_QUERY_ENGINE_QUEUES	2
>   
>   	/*
>   	 * When set to zero by userspace, this is filled with the size of the
> @@ -1734,6 +1735,31 @@ struct drm_i915_query_topology_info {
>   	__u8 data[];
>   };
>   
> +/**
> + * struct drm_i915_query_engine_queues
> + *
> + * Engine queues query enables userspace to query current counts of active
> + * requests in their different states.
> + */
> +struct drm_i915_query_engine_queues {
> +	/** Engine class as in enum drm_i915_gem_engine_class. */
> +	__u16 class;
> +
> +	/** Engine instance number. */
> +	__u16 instance;
> +
> +	/** Number of requests with unresolved fences and dependencies. */
> +	__u32 queued;
> +
> +	/** Number of ready requests waiting on a slot on GPU. */
> +	__u32 runnable;
> +
> +	/** Number of requests executing on the GPU. */
> +	__u32 running;
> +
> +	__u32 rsvd[5];
> +};
> +
>   #if defined(__cplusplus)
>   }
>   #endif