On Wed, Nov 18, 2015 at 09:56:06AM +0000, Chris Wilson wrote:
> Limit busywaiting only to the request currently being processed by the
> GPU. If the request is not currently being processed by the GPU, there
> is a very low likelihood of it being completed within the 2 microsecond
> spin timeout and so we will just be wasting CPU cycles.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 2 +-
> drivers/gpu/drm/i915/i915_gem.c | 8 +++++++-
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 8afda459a26e..16095b95d2df 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2190,7 +2190,7 @@ struct drm_i915_gem_request {
> struct intel_engine_cs *ring;
>
> /** GEM sequence number associated with this request. */
> - uint32_t seqno;
> + uint32_t seqno, spin_seqno;
>
> /** Position in the ringbuffer of the start of the request */
> u32 head;
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 414150a0b8d5..af9ffa11ef44 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1193,9 +1193,14 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state)
> * takes to sleep on a request, on the order of a microsecond.
> */
>
> - if (i915_gem_request_get_ring(req)->irq_refcount)
> + if (req->ring->irq_refcount)
> return -EBUSY;
>
> + /* Only spin if we know the GPU is processing this request */
> + if (i915_seqno_passed(req->ring->get_seqno(req->ring, false),
> + req->spin_seqno))
> + return -EAGAIN;
> +
> timeout = local_clock_us(&cpu) + 2;
> while (!need_resched()) {
> if (i915_gem_request_completed(req, true))
> @@ -2592,6 +2597,7 @@ void __i915_add_request(struct drm_i915_gem_request *request,
> request->batch_obj = obj;
>
> request->emitted_jiffies = jiffies;
> + request->spin_seqno = ring->last_submitted_seqno;
> ring->last_submitted_seqno = request->seqno;
> list_add_tail(&request->list, &ring->request_list);
>
> --
> 2.6.2
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/intel-gfx
