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)
Is there no way to get rid of the gpu_idle? Imo doing a gpu idle as part
of the cleanup of a retired request is just not great and has a good
chance to trip us up all over the place since it's _really_ unexpected.
So if we can do it (and iirc we've agreed that all the ppgtt cleanup is
mostly fluff) then I prefer we remove the root-cause instead of just
chopping off another head of the hydra.
-Daniel
>
> 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 <ch...@chris-wilson.co.uk>
> ---
> 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@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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