We need to exercise the HW and submission paths for switching contexts
rapidly to check that features such as execlists' wa_tail are adequate.
Plus it's an interesting baseline latency metric.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
.../gpu/drm/i915/selftests/i915_gem_context.c | 185 ++++++++++++++++++
1 file changed, 185 insertions(+)
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
index 1c92560d35da..d8004bf5a4f0 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
@@ -22,6 +22,8 @@
*
*/
+#include <linux/prime_numbers.h>
+
#include "../i915_selftest.h"
#include "i915_random.h"
#include "igt_flush_test.h"
@@ -32,6 +34,188 @@
#define DW_PER_PAGE (PAGE_SIZE / sizeof(u32))
+struct live_test {
+ struct drm_i915_private *i915;
+ const char *func;
+ const char *name;
+
+ unsigned int reset_count;
+};
+
+static int begin_live_test(struct live_test *t,
+ struct drm_i915_private *i915,
+ const char *func,
+ const char *name)
+{
+ int err;
+
+ t->i915 = i915;
+ t->func = func;
+ t->name = name;
+
+ err = i915_gem_wait_for_idle(i915,
+ I915_WAIT_LOCKED,
+ MAX_SCHEDULE_TIMEOUT);
+ if (err) {
+ pr_err("%s(%s): failed to idle before, with err=%d!",
+ func, name, err);
+ return err;
+ }
+
+ i915->gpu_error.missed_irq_rings = 0;
+ t->reset_count = i915_reset_count(&i915->gpu_error);
+
+ return 0;
+}
+
+static int end_live_test(struct live_test *t)
+{
+ struct drm_i915_private *i915 = t->i915;
+
+ i915_retire_requests(i915);
+
+ if (wait_for(intel_engines_are_idle(i915), 10)) {
+ pr_err("%s(%s): GPU not idle\n", t->func, t->name);
+ return -EIO;
+ }
+
+ if (t->reset_count != i915_reset_count(&i915->gpu_error)) {
+ pr_err("%s(%s): GPU was reset %d times!\n",
+ t->func, t->name,
+ i915_reset_count(&i915->gpu_error) - t->reset_count);
+ return -EIO;
+ }
+
+ if (i915->gpu_error.missed_irq_rings) {
+ pr_err("%s(%s): Missed interrupts on engines %lx\n",
+ t->func, t->name, i915->gpu_error.missed_irq_rings);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int live_nop_switch(void *arg)
+{
+ const unsigned int nctx = 1024;
+ struct drm_i915_private *i915 = arg;
+ struct intel_engine_cs *engine;
+ struct i915_gem_context **ctx;
+ enum intel_engine_id id;
+ struct drm_file *file;
+ struct live_test t;
+ unsigned long n;
+ int err = -ENODEV;
+
+ /*
+ * Create as many contexts as we can feasibly get away with
+ * and check we can switch between them rapidly.
+ *
+ * Serves as very simple stress test for submission and HW switching
+ * between contexts.
+ */
+
+ if (!DRIVER_CAPS(i915)->has_logical_contexts)
+ return 0;
+
+ file = mock_file(i915);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ mutex_lock(&i915->drm.struct_mutex);
+
+ ctx = kcalloc(sizeof(*ctx), nctx, GFP_KERNEL);
+ if (!ctx) {
+ err = -ENOMEM;
+ goto out_unlock;
+ }
+
+ for (n = 0; n < nctx; n++) {
+ ctx[n] = i915_gem_create_context(i915, file->driver_priv);
+ if (IS_ERR(ctx[n])) {
+ err = PTR_ERR(ctx[n]);
+ goto out_unlock;
+ }
+ }
+
+ for_each_engine(engine, i915, id) {
+ struct i915_request *request;
+ unsigned long end_time, prime;
+ ktime_t times[2] = {};
+
+ times[0] = ktime_get_raw();
+ for (n = 0; n < nctx; n++) {
+ request = i915_request_alloc(engine, ctx[n]);
+ i915_request_add(request);
+ }
+ i915_request_wait(request,
+ I915_WAIT_LOCKED,
+ MAX_SCHEDULE_TIMEOUT);
+ times[1] = ktime_get_raw();
+
+ pr_info("Populated %d contexts on %s in %lluns\n",
+ nctx, engine->name, ktime_to_ns(times[1] - times[0]));
+
+ err = begin_live_test(&t, i915, __func__, engine->name);
+ if (err)
+ goto out_unlock;
+
+ end_time = jiffies + i915_selftest.timeout_jiffies;
+ for_each_prime_number_from(prime, 2, 8192) {
+ times[1] = ktime_get_raw();
+
+ for (n = 0; n < prime; n++) {
+ request = i915_request_alloc(engine,
+ ctx[n % nctx]);
+ if (IS_ERR(request)) {
+ err = PTR_ERR(request);
+ goto out_unlock;
+ }
+
+ /*
+ * This space is left intentionally blank.
+ *
+ * We do not actually want to perform any
+ * action with this request, we just want
+ * to measure the latency in allocation
+ * and submission of our breadcrumbs -
+ * ensuring that the bare request is sufficient
+ * for the system to work (i.e. proper HEAD
+ * tracking of the rings, interrupt handling,
+ * etc). It also gives us the lowest bounds
+ * for latency.
+ */
+
+ i915_request_add(request);
+ }
+ i915_request_wait(request,
+ I915_WAIT_LOCKED,
+ MAX_SCHEDULE_TIMEOUT);
+
+ times[1] = ktime_sub(ktime_get_raw(), times[1]);
+ if (prime == 2)
+ times[0] = times[1];
+
+ if (__igt_timeout(end_time, NULL))
+ break;
+ }
+
+ err = end_live_test(&t);
+ if (err)
+ goto out_unlock;
+
+ pr_info("Switch latencies on %s: 1 = %lluns, %lu = %lluns\n",
+ engine->name,
+ ktime_to_ns(times[0]),
+ prime - 1, div64_u64(ktime_to_ns(times[1]), prime - 1));
+ }
+
+out_unlock:
+ mutex_unlock(&i915->drm.struct_mutex);
+ mock_file_free(i915, file);
+ return err;
+}
+
static struct i915_vma *
gpu_fill_dw(struct i915_vma *vma, u64 offset, unsigned long count, u32 value)
{
@@ -713,6 +897,7 @@ int i915_gem_context_live_selftests(struct drm_i915_private *dev_priv)
{
static const struct i915_subtest tests[] = {
SUBTEST(igt_switch_to_kernel_context),
+ SUBTEST(live_nop_switch),
SUBTEST(igt_ctx_exec),
SUBTEST(igt_ctx_readonly),
};
--
2.19.0.rc1
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