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drm/i915: add infrastructure to hold off preemption on a request
We want to set this flag in the next commit on requests containing perf queries so that the result of the perf query can just be a delta of global counters, rather than doing post processing of the OA buffer. Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> [ickle: add basic selftest for nopreempt] Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190709164227.25859-1-chris@chris-wilson.co.uk
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46c5847e3d
commit
2a98f4e65b
7 changed files with 161 additions and 6 deletions
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@ -258,6 +258,17 @@ static int effective_prio(const struct i915_request *rq)
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{
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int prio = rq_prio(rq);
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/*
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* If this request is special and must not be interrupted at any
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* cost, so be it. Note we are only checking the most recent request
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* in the context and so may be masking an earlier vip request. It
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* is hoped that under the conditions where nopreempt is used, this
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* will not matter (i.e. all requests to that context will be
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* nopreempt for as long as desired).
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*/
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if (i915_request_has_nopreempt(rq))
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prio = I915_PRIORITY_UNPREEMPTABLE;
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/*
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* On unwinding the active request, we give it a priority bump
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* if it has completed waiting on any semaphore. If we know that
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@ -721,6 +721,114 @@ static void preempt_client_fini(struct preempt_client *c)
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kernel_context_close(c->ctx);
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}
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static int live_nopreempt(void *arg)
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{
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struct drm_i915_private *i915 = arg;
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struct intel_engine_cs *engine;
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struct preempt_client a, b;
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enum intel_engine_id id;
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intel_wakeref_t wakeref;
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int err = -ENOMEM;
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/*
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* Verify that we can disable preemption for an individual request
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* that may be being observed and not want to be interrupted.
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*/
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if (!HAS_LOGICAL_RING_PREEMPTION(i915))
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return 0;
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mutex_lock(&i915->drm.struct_mutex);
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wakeref = intel_runtime_pm_get(&i915->runtime_pm);
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if (preempt_client_init(i915, &a))
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goto err_unlock;
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if (preempt_client_init(i915, &b))
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goto err_client_a;
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b.ctx->sched.priority = I915_USER_PRIORITY(I915_PRIORITY_MAX);
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for_each_engine(engine, i915, id) {
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struct i915_request *rq_a, *rq_b;
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if (!intel_engine_has_preemption(engine))
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continue;
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engine->execlists.preempt_hang.count = 0;
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rq_a = igt_spinner_create_request(&a.spin,
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a.ctx, engine,
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MI_ARB_CHECK);
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if (IS_ERR(rq_a)) {
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err = PTR_ERR(rq_a);
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goto err_client_b;
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}
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/* Low priority client, but unpreemptable! */
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rq_a->flags |= I915_REQUEST_NOPREEMPT;
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i915_request_add(rq_a);
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if (!igt_wait_for_spinner(&a.spin, rq_a)) {
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pr_err("First client failed to start\n");
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goto err_wedged;
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}
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rq_b = igt_spinner_create_request(&b.spin,
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b.ctx, engine,
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MI_ARB_CHECK);
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if (IS_ERR(rq_b)) {
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err = PTR_ERR(rq_b);
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goto err_client_b;
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}
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i915_request_add(rq_b);
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/* B is much more important than A! (But A is unpreemptable.) */
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GEM_BUG_ON(rq_prio(rq_b) <= rq_prio(rq_a));
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/* Wait long enough for preemption and timeslicing */
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if (igt_wait_for_spinner(&b.spin, rq_b)) {
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pr_err("Second client started too early!\n");
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goto err_wedged;
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}
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igt_spinner_end(&a.spin);
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if (!igt_wait_for_spinner(&b.spin, rq_b)) {
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pr_err("Second client failed to start\n");
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goto err_wedged;
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}
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igt_spinner_end(&b.spin);
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if (engine->execlists.preempt_hang.count) {
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pr_err("Preemption recorded x%d; should have been suppressed!\n",
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engine->execlists.preempt_hang.count);
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err = -EINVAL;
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goto err_wedged;
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}
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if (igt_flush_test(i915, I915_WAIT_LOCKED))
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goto err_wedged;
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}
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err = 0;
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err_client_b:
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preempt_client_fini(&b);
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err_client_a:
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preempt_client_fini(&a);
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err_unlock:
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intel_runtime_pm_put(&i915->runtime_pm, wakeref);
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mutex_unlock(&i915->drm.struct_mutex);
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return err;
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err_wedged:
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igt_spinner_end(&b.spin);
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igt_spinner_end(&a.spin);
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i915_gem_set_wedged(i915);
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err = -EIO;
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goto err_client_b;
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}
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static int live_suppress_self_preempt(void *arg)
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{
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struct drm_i915_private *i915 = arg;
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@ -2028,6 +2136,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
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SUBTEST(live_busywait_preempt),
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SUBTEST(live_preempt),
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SUBTEST(live_late_preempt),
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SUBTEST(live_nopreempt),
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SUBTEST(live_suppress_self_preempt),
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SUBTEST(live_suppress_wait_preempt),
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SUBTEST(live_chain_preempt),
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@ -17,6 +17,16 @@ enum {
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I915_PRIORITY_NORMAL = I915_CONTEXT_DEFAULT_PRIORITY,
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I915_PRIORITY_MAX = I915_CONTEXT_MAX_USER_PRIORITY + 1,
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/*
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* Requests containing performance queries must not be preempted by
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* another context. They get scheduled with their default priority and
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* once they reach the execlist ports we ensure that they stick on the
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* HW until finished by pretending that they have maximum priority,
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* i.e. nothing can have higher priority and force us to usurp the
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* active request.
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*/
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I915_PRIORITY_UNPREEMPTABLE = INT_MAX,
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I915_PRIORITY_INVALID = INT_MIN
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};
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@ -292,7 +292,7 @@ static bool i915_request_retire(struct i915_request *rq)
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dma_fence_signal_locked(&rq->fence);
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if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags))
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i915_request_cancel_breadcrumb(rq);
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if (rq->waitboost) {
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if (i915_request_has_waitboost(rq)) {
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GEM_BUG_ON(!atomic_read(&rq->i915->gt_pm.rps.num_waiters));
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atomic_dec(&rq->i915->gt_pm.rps.num_waiters);
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}
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@ -684,7 +684,7 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
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rq->file_priv = NULL;
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rq->batch = NULL;
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rq->capture_list = NULL;
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rq->waitboost = false;
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rq->flags = 0;
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rq->execution_mask = ALL_ENGINES;
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INIT_LIST_HEAD(&rq->active_list);
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@ -216,7 +216,9 @@ struct i915_request {
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/** Time at which this request was emitted, in jiffies. */
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unsigned long emitted_jiffies;
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bool waitboost;
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unsigned long flags;
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#define I915_REQUEST_WAITBOOST BIT(0)
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#define I915_REQUEST_NOPREEMPT BIT(1)
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/** timeline->request entry for this request */
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struct list_head link;
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@ -430,6 +432,17 @@ static inline void i915_request_mark_complete(struct i915_request *rq)
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rq->hwsp_seqno = (u32 *)&rq->fence.seqno; /* decouple from HWSP */
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}
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static inline bool i915_request_has_waitboost(const struct i915_request *rq)
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{
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return rq->flags & I915_REQUEST_WAITBOOST;
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}
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static inline bool i915_request_has_nopreempt(const struct i915_request *rq)
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{
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/* Preemption should only be disabled very rarely */
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return unlikely(rq->flags & I915_REQUEST_NOPREEMPT);
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}
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bool i915_retire_requests(struct drm_i915_private *i915);
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#endif /* I915_REQUEST_H */
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@ -707,6 +707,16 @@ static inline int rq_prio(const struct i915_request *rq)
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return rq->sched.attr.priority | __NO_PREEMPTION;
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}
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static inline int effective_prio(const struct i915_request *rq)
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{
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int prio = rq_prio(rq);
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if (i915_request_has_nopreempt(rq))
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prio = I915_PRIORITY_UNPREEMPTABLE;
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return prio;
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}
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static struct i915_request *schedule_in(struct i915_request *rq, int idx)
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{
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trace_i915_request_in(rq, idx);
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@ -747,7 +757,8 @@ static void __guc_dequeue(struct intel_engine_cs *engine)
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&engine->i915->guc.preempt_work[engine->id];
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int prio = execlists->queue_priority_hint;
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if (i915_scheduler_need_preempt(prio, rq_prio(last))) {
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if (i915_scheduler_need_preempt(prio,
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effective_prio(last))) {
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intel_write_status_page(engine,
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I915_GEM_HWS_PREEMPT,
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GUC_PREEMPT_INPROGRESS);
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@ -6876,9 +6876,10 @@ void gen6_rps_boost(struct i915_request *rq)
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/* Serializes with i915_request_retire() */
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boost = false;
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spin_lock_irqsave(&rq->lock, flags);
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if (!rq->waitboost && !dma_fence_is_signaled_locked(&rq->fence)) {
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if (!i915_request_has_waitboost(rq) &&
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!dma_fence_is_signaled_locked(&rq->fence)) {
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boost = !atomic_fetch_inc(&rps->num_waiters);
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rq->waitboost = true;
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rq->flags |= I915_REQUEST_WAITBOOST;
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}
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spin_unlock_irqrestore(&rq->lock, flags);
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if (!boost)
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