[PATCH 2/2] drm/i915/execlists: Suppress mere WAIT preemption
Chris Wilson
chris at chris-wilson.co.uk
Sun Feb 3 14:52:19 UTC 2019
WAIT is occasionally suppressed by virtue of preempted requests being
promoted to NEWCLIENT iff they have not all ready received that boost.
Make this consistent for all WAIT boosts that they are not allowed to
preempt executing contexts and are merely granted the right to be at the
front of the queue for the next execution slot. This is in keeping with
the desire that the WAIT boost be a minor tweak that does not give
excessive promotion to its user and open ourselves to trivial abuse.
v2: Also protect GuC submission from false preemption loops.
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
drivers/gpu/drm/i915/intel_guc_submission.c | 2 +-
drivers/gpu/drm/i915/intel_lrc.c | 9 +-
drivers/gpu/drm/i915/selftests/igt_spinner.c | 9 +-
drivers/gpu/drm/i915/selftests/intel_lrc.c | 156 +++++++++++++++++++
4 files changed, 173 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
index 8bc8aa54aa35..9e525c909159 100644
--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -720,7 +720,7 @@ static inline int rq_prio(const struct i915_request *rq)
static inline int port_prio(const struct execlist_port *port)
{
- return rq_prio(port_request(port));
+ return rq_prio(port_request(port)) | I915_WAIT_PRIORITY;
}
static bool __guc_dequeue(struct intel_engine_cs *engine)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index a9eb0211ce77..78b1cdcdeb84 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -188,6 +188,12 @@ static inline int rq_prio(const struct i915_request *rq)
return rq->sched.attr.priority;
}
+static int effective_prio(const struct i915_request *rq)
+{
+ /* Restrict mere WAIT boosts from triggering preemption */
+ return rq_prio(rq) | I915_PRIORITY_WAIT;
+}
+
static int queue_prio(const struct intel_engine_execlists *execlists)
{
struct i915_priolist *p;
@@ -208,7 +214,7 @@ static int queue_prio(const struct intel_engine_execlists *execlists)
static inline bool need_preempt(const struct intel_engine_cs *engine,
const struct i915_request *rq)
{
- const int last_prio = rq_prio(rq);
+ int last_prio;
if (!intel_engine_has_preemption(engine))
return false;
@@ -228,6 +234,7 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
* preempt. If that hint is stale or we may be trying to preempt
* ourselves, ignore the request.
*/
+ last_prio = effective_prio(rq);
if (!__execlists_need_preempt(engine->execlists.queue_priority_hint,
last_prio))
return false;
diff --git a/drivers/gpu/drm/i915/selftests/igt_spinner.c b/drivers/gpu/drm/i915/selftests/igt_spinner.c
index 9ebd9225684e..86354e51bdd3 100644
--- a/drivers/gpu/drm/i915/selftests/igt_spinner.c
+++ b/drivers/gpu/drm/i915/selftests/igt_spinner.c
@@ -142,10 +142,17 @@ igt_spinner_create_request(struct igt_spinner *spin,
*batch++ = upper_32_bits(vma->node.start);
*batch++ = MI_BATCH_BUFFER_END; /* not reached */
- i915_gem_chipset_flush(spin->i915);
+ if (engine->emit_init_breadcrumb &&
+ rq->timeline->has_initial_breadcrumb) {
+ err = engine->emit_init_breadcrumb(rq);
+ if (err)
+ goto cancel_rq;
+ }
err = engine->emit_bb_start(rq, vma->node.start, PAGE_SIZE, 0);
+ i915_gem_chipset_flush(spin->i915);
+
cancel_rq:
if (err) {
i915_request_skip(rq, err);
diff --git a/drivers/gpu/drm/i915/selftests/intel_lrc.c b/drivers/gpu/drm/i915/selftests/intel_lrc.c
index fb35f53c9ce3..86fd4589f5f0 100644
--- a/drivers/gpu/drm/i915/selftests/intel_lrc.c
+++ b/drivers/gpu/drm/i915/selftests/intel_lrc.c
@@ -405,6 +405,161 @@ static int live_suppress_self_preempt(void *arg)
goto err_client_b;
}
+static int __i915_sw_fence_call
+dummy_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
+{
+ return NOTIFY_DONE;
+}
+
+static struct i915_request *dummy_request(struct intel_engine_cs *engine)
+{
+ struct i915_request *rq;
+
+ rq = kmalloc(sizeof(*rq), GFP_KERNEL | __GFP_ZERO);
+ if (!rq)
+ return NULL;
+
+ INIT_LIST_HEAD(&rq->active_list);
+ rq->engine = engine;
+
+ i915_sched_node_init(&rq->sched);
+
+ /* mark this request as permanently incomplete */
+ rq->fence.seqno = 1;
+ rq->hwsp_seqno = (u32 *)&rq->fence.seqno + 1;
+
+ i915_sw_fence_init(&rq->submit, dummy_notify);
+ i915_sw_fence_commit(&rq->submit);
+
+ return rq;
+}
+
+static void dummy_request_free(struct i915_request *dummy)
+{
+ i915_request_mark_complete(dummy);
+ i915_sched_node_fini(dummy->engine->i915, &dummy->sched);
+ kfree(dummy);
+}
+
+static int live_suppress_wait_preempt(void *arg)
+{
+ struct drm_i915_private *i915 = arg;
+ struct preempt_client client[4];
+ struct intel_engine_cs *engine;
+ enum intel_engine_id id;
+ intel_wakeref_t wakeref;
+ int err = -ENOMEM;
+ int i;
+
+ /*
+ * Waiters are given a little priority nudge, but not enough
+ * to actually cause any preemption. Double check that we do
+ * not needlessly generate preempt-to-idle cycles.
+ */
+
+ if (!HAS_LOGICAL_RING_PREEMPTION(i915))
+ return 0;
+
+ mutex_lock(&i915->drm.struct_mutex);
+ wakeref = intel_runtime_pm_get(i915);
+
+ if (preempt_client_init(i915, &client[0])) /* ELSP[0] */
+ goto err_unlock;
+ if (preempt_client_init(i915, &client[1])) /* ELSP[1] */
+ goto err_client_0;
+ if (preempt_client_init(i915, &client[2])) /* head of queue */
+ goto err_client_1;
+ if (preempt_client_init(i915, &client[3])) /* bystander */
+ goto err_client_2;
+
+ for_each_engine(engine, i915, id) {
+ int depth;
+
+ if (!engine->emit_init_breadcrumb)
+ continue;
+
+ for (depth = 0; depth < ARRAY_SIZE(client); depth++) {
+ struct i915_request *rq[ARRAY_SIZE(client)];
+ struct i915_request *dummy;
+
+ engine->execlists.preempt_hang.count = 0;
+
+ dummy = dummy_request(engine);
+ if (!dummy)
+ goto err_client_3;
+
+ for (i = 0; i < ARRAY_SIZE(client); i++) {
+ rq[i] = igt_spinner_create_request(&client[i].spin,
+ client[i].ctx, engine,
+ MI_NOOP);
+ if (IS_ERR(rq[i])) {
+ err = PTR_ERR(rq[i]);
+ goto err_wedged;
+ }
+
+ /* Disable NEWCLIENT promotion */
+ i915_gem_active_set(&rq[i]->timeline->last_request,
+ dummy);
+ i915_request_add(rq[i]);
+ }
+
+ dummy_request_free(dummy);
+
+ GEM_BUG_ON(i915_request_completed(rq[0]));
+ if (!igt_wait_for_spinner(&client[0].spin, rq[0])) {
+ pr_err("First client failed to start\n");
+ goto err_wedged;
+ }
+ GEM_BUG_ON(!i915_request_started(rq[0]));
+
+ if (i915_request_wait(rq[depth],
+ I915_WAIT_LOCKED |
+ I915_WAIT_PRIORITY,
+ 1) != -ETIME) {
+ pr_err("Waiter depth:%d completed!\n", depth);
+ goto err_wedged;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(client); i++)
+ igt_spinner_end(&client[i].spin);
+
+ if (igt_flush_test(i915, I915_WAIT_LOCKED))
+ goto err_wedged;
+
+ if (engine->execlists.preempt_hang.count) {
+ pr_err("Preemption recorded x%d, depth %d; should have been suppressed!\n",
+ engine->execlists.preempt_hang.count,
+ depth);
+ err = -EINVAL;
+ goto err_client_3;
+ }
+ }
+ }
+
+ err = 0;
+err_client_3:
+ preempt_client_fini(&client[3]);
+err_client_2:
+ preempt_client_fini(&client[2]);
+err_client_1:
+ preempt_client_fini(&client[1]);
+err_client_0:
+ preempt_client_fini(&client[0]);
+err_unlock:
+ if (igt_flush_test(i915, I915_WAIT_LOCKED))
+ err = -EIO;
+ intel_runtime_pm_put(i915, wakeref);
+ mutex_unlock(&i915->drm.struct_mutex);
+ return err;
+
+err_wedged:
+ for (i = 0; i < ARRAY_SIZE(client); i++)
+ igt_spinner_end(&client[i].spin);
+ i915_gem_set_wedged(i915);
+ err = -EIO;
+ goto err_client_3;
+}
+
static int live_preempt_hang(void *arg)
{
struct drm_i915_private *i915 = arg;
@@ -785,6 +940,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
SUBTEST(live_preempt),
SUBTEST(live_late_preempt),
SUBTEST(live_suppress_self_preempt),
+ SUBTEST(live_suppress_wait_preempt),
SUBTEST(live_preempt_hang),
SUBTEST(live_preempt_smoke),
};
--
2.20.1
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