[Intel-gfx] [RFC 6/8] drm/i915: Expose per-engine client busyness

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-01-10 13:30:47)
> +static ssize_t
> +show_client_busy(struct device *kdev, struct device_attribute *attr, char *buf)
> +{
> +       struct i915_engine_busy_attribute *i915_attr =
> +               container_of(attr, typeof(*i915_attr), attr);
> +       struct list_head *list = &i915_attr->client->ctx_list;
> +       unsigned int engine_class = i915_attr->engine_class;
> +       struct i915_gem_context *ctx;
> +       u64 total = 0;
> +
> +       if (i915_attr->no_busy_stats)
> +               return -ENODEV;
> +
> +       rcu_read_lock();
> +       list_for_each_entry_rcu(ctx, list, client_link)
> +               total += sw_busy_add(ctx, engine_class);
> +       rcu_read_unlock();
> +
> +       return snprintf(buf, PAGE_SIZE, "%llu\n", total);
> +}
> +
> +static const char *uabi_class_names[] = {
> +       [I915_ENGINE_CLASS_RENDER] = "0",
> +       [I915_ENGINE_CLASS_COPY] = "1",
> +       [I915_ENGINE_CLASS_VIDEO] = "2",
> +       [I915_ENGINE_CLASS_VIDEO_ENHANCE] = "3",
> +};

Hmm. /sys/class/drm/card0/clients/0/busy/0

Ok. I was worried this was 0/0 and so very bland and liable to clash
later.

> +
>  int
>  __i915_drm_client_register(struct i915_drm_client *client,
>                            struct task_struct *task)
>  {
>         struct i915_drm_clients *clients = client->clients;
> +       struct drm_i915_private *i915 =
> +               container_of(clients, typeof(*i915), clients);
> +       struct intel_engine_cs *engine;
>         struct device_attribute *attr;
> -       int ret = -ENOMEM;
> +       int i, ret = -ENOMEM;
>         char idstr[32];
>  
>         if (!clients->root)
> @@ -77,10 +130,71 @@ __i915_drm_client_register(struct i915_drm_client *client,
>         if (ret)
>                 goto err_attr;
>  
> +       if (HAS_LOGICAL_RING_CONTEXTS(i915)) {
> +               client->busy_root =
> +                       kobject_create_and_add("busy", client->root);
> +               if (!client->busy_root)
> +                       goto err_attr;
> +
> +               for (i = 0; i < ARRAY_SIZE(uabi_class_names); i++) {
> +                       struct i915_engine_busy_attribute *i915_attr =
> +                               &client->attr.busy[i];


if (!intel_engine_lookup_user(i915, i, 0))
	continue;

i.e. skip if we don't have any engines of that class in the system.

> +
> +                       i915_attr->client = client;
> +                       i915_attr->engine_class = i;
> +
> +                       attr = &i915_attr->attr;
> +
> +                       sysfs_attr_init(&attr->attr);
> +
> +                       attr->attr.name = uabi_class_names[i];
> +                       attr->attr.mode = 0444;
> +                       attr->show = show_client_busy;
> +
> +                       ret = sysfs_create_file(client->busy_root,
> +                                               (struct attribute *)attr);
> +                       if (ret)
> +                               goto err_busy;
> +               }
> +
> +               /* Enable busy stats on all engines. */
> +               i = 0;
> +               for_each_uabi_engine(engine, i915) {
> +                       ret = intel_enable_engine_stats(engine);

Hmm. We gave it a global bit in 

	i915->caps.scheduler & I915_SCHEDULER_CAP_ENABLED.

That'll avoid having to do the individual checking and rollback.
-Chris