An important property for multi-client systems is that each client gets
a 'fair' allotment of system time. (Where fairness is at the whim of the
context properties, such as priorities.) This test forks N independent
clients (albeit they happen to share a single vm), and does an equal
amount of work in client and asserts that they take an equal amount of
time.
Though we have never claimed to have a completely fair scheduler, that
is what is expected.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Ramalingam C <ramalingam.c@xxxxxxxxx>
---
tests/i915/gem_exec_schedule.c | 253 +++++++++++++++++++++++++++++++++
1 file changed, 253 insertions(+)
diff --git a/tests/i915/gem_exec_schedule.c b/tests/i915/gem_exec_schedule.c
index 56c638833..d58d926b1 100644
--- a/tests/i915/gem_exec_schedule.c
+++ b/tests/i915/gem_exec_schedule.c
@@ -2495,6 +2495,254 @@ static void measure_semaphore_power(int i915)
rapl_close(&pkg);
}
+static int read_timestamp_frequency(int i915)
+{
+ int value = 0;
+ drm_i915_getparam_t gp = {
+ .value = &value,
+ .param = I915_PARAM_CS_TIMESTAMP_FREQUENCY,
+ };
+ ioctl(i915, DRM_IOCTL_I915_GETPARAM, &gp);
+ return value;
+}
+
+static uint64_t div64_u64_round_up(uint64_t x, uint64_t y)
+{
+ return (x + y - 1) / y;
+}
+
+static uint64_t ns_to_ticks(int i915, uint64_t ns)
+{
+ return div64_u64_round_up(ns * read_timestamp_frequency(i915),
+ 1000000000);
+}
+
+#define MI_INSTR(opcode, flags) (((opcode) << 23) | (flags))
+
+#define MI_MATH(x) MI_INSTR(0x1a, (x) - 1)
+#define MI_MATH_INSTR(opcode, op1, op2) ((opcode) << 20 | (op1) << 10 | (op2))
+/* Opcodes for MI_MATH_INSTR */
+#define MI_MATH_NOOP MI_MATH_INSTR(0x000, 0x0, 0x0)
+#define MI_MATH_LOAD(op1, op2) MI_MATH_INSTR(0x080, op1, op2)
+#define MI_MATH_LOADINV(op1, op2) MI_MATH_INSTR(0x480, op1, op2)
+#define MI_MATH_LOAD0(op1) MI_MATH_INSTR(0x081, op1)
+#define MI_MATH_LOAD1(op1) MI_MATH_INSTR(0x481, op1)
+#define MI_MATH_ADD MI_MATH_INSTR(0x100, 0x0, 0x0)
+#define MI_MATH_SUB MI_MATH_INSTR(0x101, 0x0, 0x0)
+#define MI_MATH_AND MI_MATH_INSTR(0x102, 0x0, 0x0)
+#define MI_MATH_OR MI_MATH_INSTR(0x103, 0x0, 0x0)
+#define MI_MATH_XOR MI_MATH_INSTR(0x104, 0x0, 0x0)
+#define MI_MATH_STORE(op1, op2) MI_MATH_INSTR(0x180, op1, op2)
+#define MI_MATH_STOREINV(op1, op2) MI_MATH_INSTR(0x580, op1, op2)
+/* Registers used as operands in MI_MATH_INSTR */
+#define MI_MATH_REG(x) (x)
+#define MI_MATH_REG_SRCA 0x20
+#define MI_MATH_REG_SRCB 0x21
+#define MI_MATH_REG_ACCU 0x31
+#define MI_MATH_REG_ZF 0x32
+#define MI_MATH_REG_CF 0x33
+
+#define MI_LOAD_REGISTER_REG MI_INSTR(0x2A, 1)
+
+static void async_delay(int i915,
+ const struct intel_execution_engine2 *e,
+ uint32_t handle,
+ uint64_t addr,
+ uint64_t ns)
+{
+ const int use_64b = intel_gen(intel_get_drm_devid(i915)) >= 8;
+ const uint32_t base = gem_engine_mmio_base(i915, e->name);
+#define CS_GPR(x) (base + 0x600 + 8 * (x))
+#define TIMESTAMP (base + 0x3a8)
+ enum { START_TS, NOW_TS };
+ uint32_t *map, *cs, *jmp;
+
+ igt_require(base);
+
+ cs = map = gem_mmap__device_coherent(i915, handle, 0, 4096, PROT_WRITE);
+
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(START_TS) + 4;
+ *cs++ = 0;
+ *cs++ = MI_LOAD_REGISTER_REG;
+ *cs++ = TIMESTAMP;
+ *cs++ = CS_GPR(START_TS);
+
+ if (offset_in_page(cs) & 4)
+ *cs++ = 0;
+ jmp = cs;
+
+ *cs++ = 0x5 << 23; /* MI_ARB_CHECK */
+
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(NOW_TS) + 4;
+ *cs++ = 0;
+ *cs++ = MI_LOAD_REGISTER_REG;
+ *cs++ = TIMESTAMP;
+ *cs++ = CS_GPR(NOW_TS);
+
+ *cs++ = MI_MATH(4);
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCA, MI_MATH_REG(NOW_TS));
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCB, MI_MATH_REG(START_TS));
+ *cs++ = MI_MATH_SUB;
+ *cs++ = MI_MATH_STOREINV(MI_MATH_REG(NOW_TS), MI_MATH_REG_ACCU);
+
+ *cs++ = 0x24 << 23 | (1 + use_64b); /* SRM */
+ *cs++ = CS_GPR(NOW_TS);
+ *cs++ = addr + 4000;
+ *cs++ = addr >> 32;
+
+ *cs++ = MI_COND_BATCH_BUFFER_END | MI_DO_COMPARE | (1 + use_64b);
+ *cs++ = ~ns_to_ticks(i915, ns);
+ *cs++ = addr + 4000;
+ *cs++ = addr >> 32;
+
+ *cs++ = MI_BATCH_BUFFER_START | 1 << 8 | use_64b;
+ *cs++ = addr + offset_in_page(jmp);
+ *cs++ = addr >> 32;
+
+ munmap(map, 4096);
+}
+
+static struct drm_i915_gem_exec_object2
+timed_create(int i915, uint32_t ctx,
+ const struct intel_execution_engine2 *e,
+ uint64_t target_ns)
+{
+ struct drm_i915_gem_exec_object2 obj = {
+ .handle = batch_create(i915),
+ .flags = EXEC_OBJECT_SUPPORTS_48B_ADDRESS,
+ };
+ struct drm_i915_gem_execbuffer2 execbuf = {
+ .buffers_ptr = to_user_pointer(&obj),
+ .buffer_count = 1,
+ .rsvd1 = ctx,
+ .flags = e->flags,
+ };
+
+ gem_execbuf(i915, &execbuf);
+ gem_sync(i915, obj.handle);
+
+ async_delay(i915, e, obj.handle, obj.offset, target_ns);
+
+ obj.flags |= EXEC_OBJECT_PINNED;
+ return obj;
+}
+
+static void fair_child(int i915, uint32_t ctx,
+ const struct intel_execution_engine2 *e,
+ uint64_t frame_ns,
+ int timeout,
+ unsigned int flags,
+ unsigned long *out)
+#define F_PACING 0x1
+{
+ const int batches_per_frame = 3;
+ struct drm_i915_gem_exec_object2 prev =
+ timed_create(i915, ctx, e, frame_ns / batches_per_frame);
+ struct drm_i915_gem_exec_object2 next =
+ timed_create(i915, ctx, e, frame_ns / batches_per_frame);
+ struct timespec tv = {};
+ unsigned long count = 0;
+ int p_fence = -1, n_fence = -1;
+
+ igt_nsec_elapsed(&tv);
+ igt_until_timeout(timeout) {
+ struct drm_i915_gem_execbuffer2 execbuf = {
+ .buffers_ptr = to_user_pointer(&next),
+ .buffer_count = 1,
+ .rsvd1 = ctx,
+ .flags = e->flags,
+ };
+
+ execbuf.flags |= I915_EXEC_FENCE_OUT;
+ gem_execbuf_wr(i915, &execbuf);
+ n_fence = execbuf.rsvd2 >> 32;
+ execbuf.flags &= ~I915_EXEC_FENCE_OUT;
+ for (int n = 1; n < batches_per_frame; n++)
+ gem_execbuf(i915, &execbuf);
+
+ if (flags & F_PACING && p_fence != -1) {
+ struct pollfd pfd = {
+ .fd = p_fence,
+ .events = POLLIN,
+ };
+ poll(&pfd, 1, -1);
+ }
+ close(p_fence);
+
+ igt_swap(prev, next);
+ igt_swap(p_fence, n_fence);
+ count++;
+ }
+ gem_sync(i915, prev.handle);
+ *out = igt_nsec_elapsed(&tv) / count;
+ close(p_fence);
+
+ gem_close(i915, next.handle);
+ gem_close(i915, prev.handle);
+}
+
+static int ul_cmp(const void *A, const void *B)
+{
+ const unsigned long *a = A, *b = B;
+
+ if (*a < *b)
+ return -1;
+ else if (*a > *b)
+ return 1;
+ else
+ return 0;
+}
+
+static void fairness(int i915,
+ const struct intel_execution_engine2 *e,
+ int timeout, unsigned int flags)
+{
+ const int frame_ns = 16666 * 1000;
+ unsigned long *result;
+
+ igt_require(intel_gen(intel_get_drm_devid(i915)) >= 8);
+
+ result = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+
+ for (int n = 2; n <= 16; n <<= 1) {
+ const int nchild = n - 1; /* odd for easy medians */
+ const int iqr_lo = nchild / 4;
+ const int iqr_hi = (3 * nchild + 3) / 4 - 1;
+ unsigned long iqr;
+
+ memset(result, 0, nchild * sizeof(result[0]));
+ igt_fork(child, nchild) {
+ uint32_t ctx = gem_context_clone_with_engines(i915, 0);
+
+
+ fair_child(i915, ctx, e, frame_ns / nchild,
+ timeout, flags, &result[child]);
+
+ gem_context_destroy(i915, ctx);
+ }
+ igt_waitchildren();
+
+ qsort(result, nchild, sizeof(*result), ul_cmp);
+ igt_info("%d clients, range: [%lu, %lu], iqr: [%lu, %lu], median: %lu\n",
+ nchild,
+ result[0], result[nchild - 1],
+ result[iqr_lo], result[iqr_hi],
+ result[nchild / 2]);
+
+ /* Median within 10% of target */
+ igt_assert(10 * result[nchild / 2] > 9 * frame_ns &&
+ 9 * result[nchild / 2] < 10 * frame_ns);
+
+ /* Variance [inter-quartile range] is less than 33% of median */
+ iqr = result[iqr_hi] - result[iqr_lo];
+ igt_assert(3 * iqr < result[nchild / 2]);
+ }
+
+ munmap(result, 4096);
+}
+
#define test_each_engine(T, i915, e) \
igt_subtest_with_dynamic(T) __for_each_physical_engine(i915, e) \
igt_dynamic_f("%s", e->name)
@@ -2589,6 +2837,11 @@ igt_main
test_each_engine_store("promotion", fd, e)
promotion(fd, e->flags);
+ test_each_engine_store("fairness", fd, e)
+ fairness(fd, e, 3, F_PACING);
+ test_each_engine_store("unfairness", fd, e)
+ fairness(fd, e, 3, 0);
+
igt_subtest_group {
igt_fixture {
igt_require(gem_scheduler_has_preemption(fd));
--
2.27.0.rc2
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