On Wed, Aug 05, 2015 at 11:25:38AM +0530, sourab.gupta@xxxxxxxxx wrote:
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 66f9ee9..08235582 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1676,6 +1676,13 @@ struct i915_oa_rcs_node {
> u32 tag;
> };
>
> +struct i915_gen_pmu_node {
> + struct list_head head;
This not the head of the list, but a node.
> + struct drm_i915_gem_request *req;
Use request since this is a less often used member name and brevity
isn't saving thousands of keystrokes.
> + u32 offset;
> + u32 ctx_id;
> +};
> +static int i915_gen_pmu_wait_gpu(struct drm_i915_private *dev_priv)
> +{
> + struct i915_gen_pmu_node *last_entry = NULL;
> + int ret;
> +
> + /*
> + * Wait for the last scheduled request to complete. This would
> + * implicitly wait for the prior submitted requests. The refcount
> + * of the requests is not decremented here.
> + */
> + spin_lock(&dev_priv->gen_pmu.lock);
> +
> + if (!list_empty(&dev_priv->gen_pmu.node_list)) {
> + last_entry = list_last_entry(&dev_priv->gen_pmu.node_list,
> + struct i915_gen_pmu_node, head);
> + }
> + spin_unlock(&dev_priv->gen_pmu.lock);
Because you issue requests on all rings that are not actually
serialised, the order of writes and retirements are also not serialised,
i.e. this does not do a complete wait for all activity on the object.
> static void forward_gen_pmu_snapshots(struct drm_i915_private *dev_priv)
> {
> - WARN_ON(!dev_priv->gen_pmu.buffer.addr);
> + struct i915_gen_pmu_node *entry, *next;
> + LIST_HEAD(deferred_list_free);
> + int ret;
>
> - /* TODO: routine for forwarding snapshots to userspace */
> + list_for_each_entry_safe
> + (entry, next, &dev_priv->gen_pmu.node_list, head) {
> + if (!i915_gem_request_completed(entry->req, true))
> + break;
Again the list is not actually in retirement order since you combine
multiple rings into one list.
These problems magically disappear with a list per-ring and a page
per-ring. You also need to be more careful with overwriting unflushed
entries. A dynamic approach to page allocation overcomes that.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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