On Mon, Jan 27, 2014 at 10:43:07PM +0000, Chris Wilson wrote:
> As the VM do not track activity of objects and instead use a large
> hammer to forcibly idle and evict all of their associated objects when
> one is released, it is possible for that to cause a recursion when we
> need to wait for free space on a ring and call retire requests.
> (intel_ring_begin -> intel_ring_wait_request ->
> i915_gem_retire_requests_ring -> i915_gem_context_free ->
> i915_gem_evict_vm -> i915_gpu_idle -> intel_ring_begin etc)
>
> In order to remove the requirement for calling retire-requests from
> intel_ring_wait_request, we have to inline a couple of steps from
> retiring requests, notably we have to record the position of the request
> we wait for and use that to update the available ring space.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Looks good to me.
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
I do have a couple of questions about request->tail though.
We set it to -1 in intel_ring_wait_request(). Isn't that going to cause
problems for i915_request_guilty()?
When not -1, request->tail points to just before the commands that
.add_request() adds to the ring. So that means intel_ring_wait_request()
might have to wait for one extra request, and I guess more importantly
if the GPU hangs inside the .add_request() commands, we won't attribute
the hang to the request in question. Was it designe to be that way, or
is there a bug here?
> ---
> drivers/gpu/drm/i915/intel_ringbuffer.c | 25 +++++--------------------
> 1 file changed, 5 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 10ff32d09c14..0da7c257159a 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1431,28 +1431,16 @@ void intel_cleanup_ring_buffer(struct intel_ring_buffer *ring)
> cleanup_status_page(ring);
> }
>
> -static int intel_ring_wait_seqno(struct intel_ring_buffer *ring, u32 seqno)
> -{
> - int ret;
> -
> - ret = i915_wait_seqno(ring, seqno);
> - if (!ret)
> - i915_gem_retire_requests_ring(ring);
> -
> - return ret;
> -}
> -
> static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
> {
> struct drm_i915_gem_request *request;
> - u32 seqno = 0;
> + u32 seqno = 0, tail;
> int ret;
>
> - i915_gem_retire_requests_ring(ring);
> -
> if (ring->last_retired_head != -1) {
> ring->head = ring->last_retired_head;
> ring->last_retired_head = -1;
> +
> ring->space = ring_space(ring);
> if (ring->space >= n)
> return 0;
> @@ -1469,6 +1457,7 @@ static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
> space += ring->size;
> if (space >= n) {
> seqno = request->seqno;
> + tail = request->tail;
> break;
> }
>
> @@ -1483,15 +1472,11 @@ static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
> if (seqno == 0)
> return -ENOSPC;
>
> - ret = intel_ring_wait_seqno(ring, seqno);
> + ret = i915_wait_seqno(ring, seqno);
> if (ret)
> return ret;
>
> - if (WARN_ON(ring->last_retired_head == -1))
> - return -ENOSPC;
> -
> - ring->head = ring->last_retired_head;
> - ring->last_retired_head = -1;
> + ring->head = tail;
> ring->space = ring_space(ring);
> if (WARN_ON(ring->space < n))
> return -ENOSPC;
> --
> 1.8.5.3
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/intel-gfx
