drm/i915: Live testing of empty requests

Primarily to emphasize the difference between just advancing the
breadcrumb using a bare request and the overhead of dispatching an
execbuffer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170213171558.20942-16-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_request.c b/drivers/gpu/drm/i915/selftests/i915_gem_request.c
index e946488..9d056a8 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_request.c
@@ -338,6 +338,160 @@ out_unlock:
        return err;
 }
 
+static struct i915_vma *empty_batch(struct drm_i915_private *i915)
+{
+       struct drm_i915_gem_object *obj;
+       struct i915_vma *vma;
+       u32 *cmd;
+       int err;
+
+       obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
+       if (IS_ERR(obj))
+               return ERR_CAST(obj);
+
+       cmd = i915_gem_object_pin_map(obj, I915_MAP_WB);
+       if (IS_ERR(cmd)) {
+               err = PTR_ERR(cmd);
+               goto err;
+       }
+       *cmd = MI_BATCH_BUFFER_END;
+       i915_gem_object_unpin_map(obj);
+
+       err = i915_gem_object_set_to_gtt_domain(obj, false);
+       if (err)
+               goto err;
+
+       vma = i915_vma_instance(obj, &i915->ggtt.base, NULL);
+       if (IS_ERR(vma)) {
+               err = PTR_ERR(vma);
+               goto err;
+       }
+
+       err = i915_vma_pin(vma, 0, 0, PIN_USER | PIN_GLOBAL);
+       if (err)
+               goto err;
+
+       return vma;
+
+err:
+       i915_gem_object_put(obj);
+       return ERR_PTR(err);
+}
+
+static struct drm_i915_gem_request *
+empty_request(struct intel_engine_cs *engine,
+             struct i915_vma *batch)
+{
+       struct drm_i915_gem_request *request;
+       int err;
+
+       request = i915_gem_request_alloc(engine,
+                                        engine->i915->kernel_context);
+       if (IS_ERR(request))
+               return request;
+
+       err = engine->emit_flush(request, EMIT_INVALIDATE);
+       if (err)
+               goto out_request;
+
+       err = i915_switch_context(request);
+       if (err)
+               goto out_request;
+
+       err = engine->emit_bb_start(request,
+                                   batch->node.start,
+                                   batch->node.size,
+                                   I915_DISPATCH_SECURE);
+       if (err)
+               goto out_request;
+
+out_request:
+       __i915_add_request(request, err == 0);
+       return err ? ERR_PTR(err) : request;
+}
+
+static int live_empty_request(void *arg)
+{
+       struct drm_i915_private *i915 = arg;
+       struct intel_engine_cs *engine;
+       struct live_test t;
+       struct i915_vma *batch;
+       unsigned int id;
+       int err = 0;
+
+       /* Submit various sized batches of empty requests, to each engine
+        * (individually), and wait for the batch to complete. We can check
+        * the overhead of submitting requests to the hardware.
+        */
+
+       mutex_lock(&i915->drm.struct_mutex);
+
+       batch = empty_batch(i915);
+       if (IS_ERR(batch)) {
+               err = PTR_ERR(batch);
+               goto out_unlock;
+       }
+
+       for_each_engine(engine, i915, id) {
+               IGT_TIMEOUT(end_time);
+               struct drm_i915_gem_request *request;
+               unsigned long n, prime;
+               ktime_t times[2] = {};
+
+               err = begin_live_test(&t, i915, __func__, engine->name);
+               if (err)
+                       goto out_batch;
+
+               /* Warmup / preload */
+               request = empty_request(engine, batch);
+               if (IS_ERR(request)) {
+                       err = PTR_ERR(request);
+                       goto out_batch;
+               }
+               i915_wait_request(request,
+                                 I915_WAIT_LOCKED,
+                                 MAX_SCHEDULE_TIMEOUT);
+
+               for_each_prime_number_from(prime, 1, 8192) {
+                       times[1] = ktime_get_raw();
+
+                       for (n = 0; n < prime; n++) {
+                               request = empty_request(engine, batch);
+                               if (IS_ERR(request)) {
+                                       err = PTR_ERR(request);
+                                       goto out_batch;
+                               }
+                       }
+                       i915_wait_request(request,
+                                         I915_WAIT_LOCKED,
+                                         MAX_SCHEDULE_TIMEOUT);
+
+                       times[1] = ktime_sub(ktime_get_raw(), times[1]);
+                       if (prime == 1)
+                               times[0] = times[1];
+
+                       if (__igt_timeout(end_time, NULL))
+                               break;
+               }
+
+               err = end_live_test(&t);
+               if (err)
+                       goto out_batch;
+
+               pr_info("Batch latencies on %s: 1 = %lluns, %lu = %lluns\n",
+                       engine->name,
+                       ktime_to_ns(times[0]),
+                       prime, div64_u64(ktime_to_ns(times[1]), prime));
+       }
+
+out_batch:
+       i915_vma_unpin(batch);
+       i915_vma_put(batch);
+out_unlock:
+       mutex_unlock(&i915->drm.struct_mutex);
+       return err;
+}
+
 static struct i915_vma *recursive_batch(struct drm_i915_private *i915)
 {
        struct i915_gem_context *ctx = i915->kernel_context;
@@ -658,6 +812,7 @@ int i915_gem_request_live_selftests(struct drm_i915_private *i915)
                SUBTEST(live_nop_request),
                SUBTEST(live_all_engines),
                SUBTEST(live_sequential_engines),
+               SUBTEST(live_empty_request),
        };
        return i915_subtests(tests, i915);
 }