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 <ch...@chris-wilson.co.uk>
---
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
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