On Tue, Sep 13, 2016 at 11:24:52AM +0100, Tvrtko Ursulin wrote: > > On 12/09/16 15:09, Imre Deak wrote: > >While user space has control over the scheduling priority of its page > >flipping thread, the corresponding work the driver schedules for MMIO > >flips always runs with normal scheduling priority. This would hinder an > >application that wants more stringent guarantees over flip timing (to > >avoid missing a flip at the next frame count). > > > >Fix this by scheduling the work with high priority, meaning normal > >scheduling policy with -20 nice level. > > > >Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97775 > >Testcase: igt/kms_cursor_legacy > >CC: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > >CC: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > >Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> > >--- > > drivers/gpu/drm/i915/i915_drv.c | 7 +++++++ > > drivers/gpu/drm/i915/i915_drv.h | 4 ++++ > > drivers/gpu/drm/i915/intel_display.c | 2 +- > > 3 files changed, 12 insertions(+), 1 deletion(-) > > > >diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c > >index 02c34d6..381ef23 100644 > >--- a/drivers/gpu/drm/i915/i915_drv.c > >+++ b/drivers/gpu/drm/i915/i915_drv.c > >@@ -756,8 +756,14 @@ static int i915_workqueues_init(struct drm_i915_private *dev_priv) > > if (dev_priv->hotplug.dp_wq == NULL) > > goto out_free_wq; > > > >+ dev_priv->flip_wq = alloc_workqueue("i915-flip", WQ_HIGHPRI, 0); > >+ if (dev_priv->flip_wq == NULL) > >+ goto out_free_dp_wq; > >+ > > return 0; > > > >+out_free_dp_wq: > >+ destroy_workqueue(dev_priv->hotplug.dp_wq); > > out_free_wq: > > destroy_workqueue(dev_priv->wq); > > out_err: > >@@ -768,6 +774,7 @@ out_err: > > > > static void i915_workqueues_cleanup(struct drm_i915_private *dev_priv) > > { > >+ destroy_workqueue(dev_priv->flip_wq); > > destroy_workqueue(dev_priv->hotplug.dp_wq); > > destroy_workqueue(dev_priv->wq); > > } > >diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > >index f499fa5..3653ce4 100644 > >--- a/drivers/gpu/drm/i915/i915_drv.h > >+++ b/drivers/gpu/drm/i915/i915_drv.h > >@@ -1844,6 +1844,10 @@ struct drm_i915_private { > > * result in deadlocks. > > */ > > struct workqueue_struct *wq; > >+ /** > >+ * flip_wq - High priority flip workqueue. > >+ */ > >+ struct workqueue_struct *flip_wq; > > > > /* Display functions */ > > struct drm_i915_display_funcs display; > >diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > >index 3c367d0..48433e1 100644 > >--- a/drivers/gpu/drm/i915/intel_display.c > >+++ b/drivers/gpu/drm/i915/intel_display.c > >@@ -12278,7 +12278,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc, > > > > work->flip_queued_req = i915_gem_active_get(&obj->last_write, > > &obj->base.dev->struct_mutex); > >- schedule_work(&work->mmio_work); > >+ queue_work(dev_priv->flip_wq, &work->mmio_work); > > } else { > > request = i915_gem_request_alloc(engine, engine->last_context); > > if (IS_ERR(request)) { > > > > I am curious if just a dedicated wq would be enough, or you have > found that it has to be a high-prio one? > > Otherwise patch looks fine to me. The problem is that this just the tip of the iceberg. mmioflips will be driven by atomic in the near future. This isn't a viable solution as not everything in that work is suitable for high priority. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
