| Message ID | 1449833608-22125-4-git-send-email-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Dec 11, 2015 at 11:32:59AM +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. > > v2: Check for logical inversion when rebasing - we were incorrectly > checking for this request being active, and instead busywaiting for > when the GPU was not yet processing the request of interest. > > v3: Try another colour for the seqno names. > v4: Another colour for the function names. > > v5: Remove the forced coherency when checking for the active request. On > reflection and plenty of recent experimentation, the issue is not a > cache coherency problem - but an irq/seqno ordering problem (timing issue). > Here, we do not need the w/a to force ordering of the read with an > interrupt. > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> > Cc: "Rogozhkin, Dmitry V" <dmitry.v.rogozhkin@intel.com> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> > Cc: Eero Tamminen <eero.t.tamminen@intel.com> > Cc: "Rantala, Valtteri" <valtteri.rantala@intel.com> > Cc: stable@vger.kernel.org Merged these 3 patches, thanks. -Daniel > --- > drivers/gpu/drm/i915/i915_drv.h | 27 +++++++++++++++++++-------- > drivers/gpu/drm/i915/i915_gem.c | 8 +++++++- > 2 files changed, 26 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 5edd39352e97..8c4303b664d9 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -2182,8 +2182,17 @@ struct drm_i915_gem_request { > struct drm_i915_private *i915; > struct intel_engine_cs *ring; > > - /** GEM sequence number associated with this request. */ > - uint32_t seqno; > + /** GEM sequence number associated with the previous request, > + * when the HWS breadcrumb is equal to this the GPU is processing > + * this request. > + */ > + u32 previous_seqno; > + > + /** GEM sequence number associated with this request, > + * when the HWS breadcrumb is equal or greater than this the GPU > + * has finished processing this request. > + */ > + u32 seqno; > > /** Position in the ringbuffer of the start of the request */ > u32 head; > @@ -2958,15 +2967,17 @@ i915_seqno_passed(uint32_t seq1, uint32_t seq2) > return (int32_t)(seq1 - seq2) >= 0; > } > > +static inline bool i915_gem_request_started(struct drm_i915_gem_request *req, > + bool lazy_coherency) > +{ > + u32 seqno = req->ring->get_seqno(req->ring, lazy_coherency); > + return i915_seqno_passed(seqno, req->previous_seqno); > +} > + > static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req, > bool lazy_coherency) > { > - u32 seqno; > - > - BUG_ON(req == NULL); > - > - seqno = req->ring->get_seqno(req->ring, lazy_coherency); > - > + u32 seqno = req->ring->get_seqno(req->ring, lazy_coherency); > return i915_seqno_passed(seqno, req->seqno); > } > > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c > index 46a84c447d8f..29d98ddbbc80 100644 > --- a/drivers/gpu/drm/i915/i915_gem.c > +++ b/drivers/gpu/drm/i915/i915_gem.c > @@ -1193,9 +1193,13 @@ 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_gem_request_started(req, true)) > + return -EAGAIN; > + > timeout = local_clock_us(&cpu) + 5; > while (!need_resched()) { > if (i915_gem_request_completed(req, true)) > @@ -1209,6 +1213,7 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state) > > cpu_relax_lowlatency(); > } > + > if (i915_gem_request_completed(req, false)) > return 0; > > @@ -2600,6 +2605,7 @@ void __i915_add_request(struct drm_i915_gem_request *request, > request->batch_obj = obj; > > request->emitted_jiffies = jiffies; > + request->previous_seqno = ring->last_submitted_seqno; > ring->last_submitted_seqno = request->seqno; > list_add_tail(&request->list, &ring->request_list); > > -- > 2.6.3 >
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 5edd39352e97..8c4303b664d9 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2182,8 +2182,17 @@ struct drm_i915_gem_request { struct drm_i915_private *i915; struct intel_engine_cs *ring; - /** GEM sequence number associated with this request. */ - uint32_t seqno; + /** GEM sequence number associated with the previous request, + * when the HWS breadcrumb is equal to this the GPU is processing + * this request. + */ + u32 previous_seqno; + + /** GEM sequence number associated with this request, + * when the HWS breadcrumb is equal or greater than this the GPU + * has finished processing this request. + */ + u32 seqno; /** Position in the ringbuffer of the start of the request */ u32 head; @@ -2958,15 +2967,17 @@ i915_seqno_passed(uint32_t seq1, uint32_t seq2) return (int32_t)(seq1 - seq2) >= 0; } +static inline bool i915_gem_request_started(struct drm_i915_gem_request *req, + bool lazy_coherency) +{ + u32 seqno = req->ring->get_seqno(req->ring, lazy_coherency); + return i915_seqno_passed(seqno, req->previous_seqno); +} + static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req, bool lazy_coherency) { - u32 seqno; - - BUG_ON(req == NULL); - - seqno = req->ring->get_seqno(req->ring, lazy_coherency); - + u32 seqno = req->ring->get_seqno(req->ring, lazy_coherency); return i915_seqno_passed(seqno, req->seqno); } diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 46a84c447d8f..29d98ddbbc80 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1193,9 +1193,13 @@ 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_gem_request_started(req, true)) + return -EAGAIN; + timeout = local_clock_us(&cpu) + 5; while (!need_resched()) { if (i915_gem_request_completed(req, true)) @@ -1209,6 +1213,7 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state) cpu_relax_lowlatency(); } + if (i915_gem_request_completed(req, false)) return 0; @@ -2600,6 +2605,7 @@ void __i915_add_request(struct drm_i915_gem_request *request, request->batch_obj = obj; request->emitted_jiffies = jiffies; + request->previous_seqno = ring->last_submitted_seqno; ring->last_submitted_seqno = request->seqno; list_add_tail(&request->list, &ring->request_list);