drm/i915/selftests: Smoketest preemption

Very light stress test to bombard the submission backends with a large
stream with requests of randomly assigned priorities. Preemption will be
occasionally requested, but unlikely to ever succeed! (Although we may
build a long queue of requests and so may trigger an attempt to inject a
preempt context, as we emit no batch, the arbitration window is limited
to between requests inside the ringbuffer. The likelihood of actually
causing a preemption event is therefore very small. A later variant
should try to improve the likelihood of preemption events!)

v2: Include a second pattern with more frequent preemption

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180925083205.2229-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/selftests/intel_lrc.c b/drivers/gpu/drm/i915/selftests/intel_lrc.c
index 1aea7a8..3a474bb 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/intel_lrc.c
+++ b/drivers/gpu/drm/i915/selftests/intel_lrc.c
@@ -6,6 +6,7 @@
 
 #include "../i915_selftest.h"
 #include "igt_flush_test.h"
+#include "i915_random.h"
 
 #include "mock_context.h"
 
@@ -573,6 +574,141 @@ err_unlock:
        return err;
 }
 
+static int random_range(struct rnd_state *rnd, int min, int max)
+{
+       return i915_prandom_u32_max_state(max - min, rnd) + min;
+}
+
+static int random_priority(struct rnd_state *rnd)
+{
+       return random_range(rnd, I915_PRIORITY_MIN, I915_PRIORITY_MAX);
+}
+
+struct preempt_smoke {
+       struct drm_i915_private *i915;
+       struct i915_gem_context **contexts;
+       unsigned int ncontext;
+       struct rnd_state prng;
+};
+
+static struct i915_gem_context *smoke_context(struct preempt_smoke *smoke)
+{
+       return smoke->contexts[i915_prandom_u32_max_state(smoke->ncontext,
+                                                         &smoke->prng)];
+}
+
+static int smoke_crescendo(struct preempt_smoke *smoke)
+{
+       struct intel_engine_cs *engine;
+       enum intel_engine_id id;
+       unsigned long count;
+
+       count = 0;
+       for_each_engine(engine, smoke->i915, id) {
+               IGT_TIMEOUT(end_time);
+
+               do {
+                       struct i915_gem_context *ctx = smoke_context(smoke);
+                       struct i915_request *rq;
+
+                       ctx->sched.priority = count % I915_PRIORITY_MAX;
+
+                       rq = i915_request_alloc(engine, ctx);
+                       if (IS_ERR(rq))
+                               return PTR_ERR(rq);
+
+                       i915_request_add(rq);
+                       count++;
+               } while (!__igt_timeout(end_time, NULL));
+       }
+
+       pr_info("Submitted %lu crescendo requests across %d engines and %d contexts\n",
+               count, INTEL_INFO(smoke->i915)->num_rings, smoke->ncontext);
+       return 0;
+}
+
+static int smoke_random(struct preempt_smoke *smoke)
+{
+       struct intel_engine_cs *engine;
+       enum intel_engine_id id;
+       IGT_TIMEOUT(end_time);
+       unsigned long count;
+
+       count = 0;
+       do {
+               for_each_engine(engine, smoke->i915, id) {
+                       struct i915_gem_context *ctx = smoke_context(smoke);
+                       struct i915_request *rq;
+
+                       ctx->sched.priority = random_priority(&smoke->prng);
+
+                       rq = i915_request_alloc(engine, ctx);
+                       if (IS_ERR(rq))
+                               return PTR_ERR(rq);
+
+                       i915_request_add(rq);
+                       count++;
+               }
+       } while (!__igt_timeout(end_time, NULL));
+
+       pr_info("Submitted %lu random requests across %d engines and %d contexts\n",
+               count, INTEL_INFO(smoke->i915)->num_rings, smoke->ncontext);
+       return 0;
+}
+
+static int live_preempt_smoke(void *arg)
+{
+       struct preempt_smoke smoke = {
+               .i915 = arg,
+               .prng = I915_RND_STATE_INITIALIZER(i915_selftest.random_seed),
+               .ncontext = 1024,
+       };
+       int err = -ENOMEM;
+       int n;
+
+       if (!HAS_LOGICAL_RING_PREEMPTION(smoke.i915))
+               return 0;
+
+       smoke.contexts = kmalloc_array(smoke.ncontext,
+                                      sizeof(*smoke.contexts),
+                                      GFP_KERNEL);
+       if (!smoke.contexts)
+               return -ENOMEM;
+
+       mutex_lock(&smoke.i915->drm.struct_mutex);
+       intel_runtime_pm_get(smoke.i915);
+
+       for (n = 0; n < smoke.ncontext; n++) {
+               smoke.contexts[n] = kernel_context(smoke.i915);
+               if (!smoke.contexts[n])
+                       goto err_ctx;
+       }
+
+       err = smoke_crescendo(&smoke);
+       if (err)
+               goto err_ctx;
+
+       err = smoke_random(&smoke);
+       if (err)
+               goto err_ctx;
+
+err_ctx:
+       if (igt_flush_test(smoke.i915, I915_WAIT_LOCKED))
+               err = -EIO;
+
+       for (n = 0; n < smoke.ncontext; n++) {
+               if (!smoke.contexts[n])
+                       break;
+               kernel_context_close(smoke.contexts[n]);
+       }
+
+       intel_runtime_pm_put(smoke.i915);
+       mutex_unlock(&smoke.i915->drm.struct_mutex);
+       kfree(smoke.contexts);
+
+       return err;
+}
+
 int intel_execlists_live_selftests(struct drm_i915_private *i915)
 {
        static const struct i915_subtest tests[] = {
@@ -580,6 +716,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
                SUBTEST(live_preempt),
                SUBTEST(live_late_preempt),
                SUBTEST(live_preempt_hang),
+               SUBTEST(live_preempt_smoke),
        };
 
        if (!HAS_EXECLISTS(i915))