On 02/18/2016 06:26 AM, John.C.Harrison@xxxxxxxxx wrote:
> From: John Harrison <John.C.Harrison@xxxxxxxxx>
>
> A major point of the GPU scheduler is that it re-orders batch buffers
> after they have been submitted to the driver. This leads to requests
> completing out of order. In turn, this means that the retire
> processing can no longer assume that all completed entries are at the
> front of the list. Rather than attempting to re-order the request list
> on a regular basis, it is better to simply scan the entire list.
>
> v2: Removed deferred free code as no longer necessary due to request
> handling updates.
>
> For: VIZ-1587
> Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 31 +++++++++++++------------------
> 1 file changed, 13 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 7d9aa24..0003cfc 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3233,6 +3233,7 @@ void i915_gem_reset(struct drm_device *dev)
> void
> i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
> {
> + struct drm_i915_gem_object *obj, *obj_next;
> struct drm_i915_gem_request *req, *req_next;
> LIST_HEAD(list_head);
>
> @@ -3245,37 +3246,31 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
> */
> i915_gem_request_notify(ring, false);
>
> + /*
> + * Note that request entries might be out of order due to rescheduling
> + * and pre-emption. Thus both lists must be processed in their entirety
> + * rather than stopping at the first non-complete entry.
> + */
> +
> /* Retire requests first as we use it above for the early return.
> * If we retire requests last, we may use a later seqno and so clear
> * the requests lists without clearing the active list, leading to
> * confusion.
> */
> - while (!list_empty(&ring->request_list)) {
> - struct drm_i915_gem_request *request;
> -
> - request = list_first_entry(&ring->request_list,
> - struct drm_i915_gem_request,
> - list);
> -
> - if (!i915_gem_request_completed(request))
> - break;
> + list_for_each_entry_safe(req, req_next, &ring->request_list, list) {
> + if (!i915_gem_request_completed(req))
> + continue;
>
> - i915_gem_request_retire(request);
> + i915_gem_request_retire(req);
> }
>
> /* Move any buffers on the active list that are no longer referenced
> * by the ringbuffer to the flushing/inactive lists as appropriate,
> * before we free the context associated with the requests.
> */
> - while (!list_empty(&ring->active_list)) {
> - struct drm_i915_gem_object *obj;
> -
> - obj = list_first_entry(&ring->active_list,
> - struct drm_i915_gem_object,
> - ring_list[ring->id]);
> -
> + list_for_each_entry_safe(obj, obj_next, &ring->active_list, ring_list[ring->id]) {
> if (!list_empty(&obj->last_read_req[ring->id]->list))
> - break;
> + continue;
>
> i915_gem_object_retire__read(obj, ring->id);
> }
>
Reviewed-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
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