[Intel-gfx] [PATCH i-g-t] i915/gem_exec_schedule: Try to spot unfairness
Chris Wilson
chris at chris-wilson.co.uk
Tue Jun 2 00:26:50 UTC 2020
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 at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Ramalingam C <ramalingam.c at intel.com>
---
tests/i915/gem_exec_schedule.c | 418 +++++++++++++++++++++++++++++++++
1 file changed, 418 insertions(+)
diff --git a/tests/i915/gem_exec_schedule.c b/tests/i915/gem_exec_schedule.c
index 56c638833..d1121ecd2 100644
--- a/tests/i915/gem_exec_schedule.c
+++ b/tests/i915/gem_exec_schedule.c
@@ -2495,6 +2495,417 @@ 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),
+ NSEC_PER_SEC);
+}
+
+static uint64_t ticks_to_ns(int i915, uint64_t ticks)
+{
+ return div64_u64_round_up(ticks * NSEC_PER_SEC,
+ read_timestamp_frequency(i915));
+}
+
+#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 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
+delay_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);
+
+ delay(i915, e, obj.handle, obj.offset, target_ns);
+
+ obj.flags |= EXEC_OBJECT_PINNED;
+ return obj;
+}
+
+static void tslog(int i915,
+ const struct intel_execution_engine2 *e,
+ uint32_t handle,
+ uint64_t addr)
+{
+ 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 CS_TIMESTAMP (base + 0x358)
+ enum { ONE, MASK, ADDR };
+ uint32_t *timestamp_lo, *addr_lo;
+ uint32_t *map, *cs;
+
+ igt_require(base);
+
+ map = gem_mmap__device_coherent(i915, handle, 0, 4096, PROT_WRITE);
+ cs = map + 512;
+
+ *cs++ = 0x24 << 23 | (1 + use_64b); /* SRM */
+ *cs++ = CS_TIMESTAMP;
+ timestamp_lo = cs;
+ *cs++ = addr;
+ *cs++ = addr >> 32;
+
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(ADDR);
+ addr_lo = cs;
+ *cs++ = addr;
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(ADDR) + 4;
+ *cs++ = addr >> 32;
+
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(ONE);
+ *cs++ = 4;
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(ONE) + 4;
+ *cs++ = 0;
+
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(MASK);
+ *cs++ = 0xfffff7ff;
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(MASK) + 4;
+ *cs++ = 0xffffffff;
+
+ *cs++ = MI_MATH(8);
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCA, MI_MATH_REG(ONE));
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCB, MI_MATH_REG(ADDR));
+ *cs++ = MI_MATH_ADD;
+ *cs++ = MI_MATH_STORE(MI_MATH_REG(ADDR), MI_MATH_REG_ACCU);
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCA, MI_MATH_REG(ADDR));
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCB, MI_MATH_REG(MASK));
+ *cs++ = MI_MATH_AND;
+ *cs++ = MI_MATH_STORE(MI_MATH_REG(ADDR), MI_MATH_REG_ACCU);
+
+ *cs++ = 0x24 << 23 | (1 + use_64b); /* SRM */
+ *cs++ = CS_GPR(ADDR);
+ *cs++ = addr + offset_in_page(timestamp_lo);
+ *cs++ = addr >> 32;
+ *cs++ = 0x24 << 23 | (1 + use_64b); /* SRM */
+ *cs++ = CS_GPR(ADDR);
+ *cs++ = addr + offset_in_page(addr_lo);
+ *cs++ = addr >> 32;
+
+ *cs++ = MI_BATCH_BUFFER_END;
+
+ munmap(map, 4096);
+}
+
+static struct drm_i915_gem_exec_object2
+tslog_create(int i915, uint32_t ctx, const struct intel_execution_engine2 *e)
+{
+ 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);
+
+ tslog(i915, e, obj.handle, obj.offset);
+
+ obj.flags |= EXEC_OBJECT_PINNED;
+ return obj;
+}
+
+static int cmp_u32(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 fair_child(int i915, uint32_t ctx,
+ const struct intel_execution_engine2 *e,
+ uint64_t frame_ns,
+ int timeout,
+ int timeline,
+ unsigned int flags,
+ unsigned long *ctl,
+ unsigned long *out)
+#define F_PACING 0x1
+#define F_EXTERNAL 0x2
+{
+ const int batches_per_frame = 3;
+ struct drm_i915_gem_exec_object2 prev =
+ delay_create(i915, ctx, e, frame_ns / batches_per_frame);
+ struct drm_i915_gem_exec_object2 next =
+ delay_create(i915, ctx, e, frame_ns / batches_per_frame);
+ struct drm_i915_gem_exec_object2 ts = tslog_create(i915, ctx, e);
+ struct timespec tv = {};
+ unsigned long count = 0;
+ int p_fence = -1, n_fence = -1;
+ uint32_t *map;
+ int n;
+
+ igt_nsec_elapsed(&tv);
+ while (!READ_ONCE(*ctl)) {
+ struct drm_i915_gem_execbuffer2 execbuf = {
+ .buffers_ptr = to_user_pointer(&next),
+ .buffer_count = 1,
+ .rsvd1 = ctx,
+ .rsvd2 = -1,
+ .flags = e->flags,
+ };
+
+ if (flags & F_EXTERNAL) {
+ execbuf.rsvd2 =
+ sw_sync_timeline_create_fence(timeline, count);
+ execbuf.flags |= I915_EXEC_FENCE_IN;
+ }
+
+ execbuf.flags |= I915_EXEC_FENCE_OUT;
+ gem_execbuf_wr(i915, &execbuf);
+ n_fence = execbuf.rsvd2 >> 32;
+ execbuf.flags &= ~(I915_EXEC_FENCE_OUT | I915_EXEC_FENCE_IN);
+ for (n = 1; n < batches_per_frame; n++)
+ gem_execbuf(i915, &execbuf);
+
+ execbuf.buffers_ptr = to_user_pointer(&ts);
+ execbuf.batch_start_offset = 2048;
+ 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);
+ close(execbuf.rsvd2);
+
+ igt_swap(prev, next);
+ igt_swap(p_fence, n_fence);
+ count++;
+ }
+ gem_sync(i915, prev.handle);
+ close(p_fence);
+
+ gem_close(i915, next.handle);
+ gem_close(i915, prev.handle);
+
+ map = gem_mmap__device_coherent(i915, ts.handle, 0, 4096, PROT_WRITE);
+ for (n = 1; n < min(count, 512); n++)
+ map[n - 1] = map[n] - map[n - 1];
+ qsort(map, --n, sizeof(*map), cmp_u32);
+ *out = ticks_to_ns(i915, map[n / 2]);
+ munmap(map, 4096);
+
+ gem_close(i915, ts.handle);
+}
+
+static int cmp_ul(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);
+ igt_require(gem_class_has_mutable_submission(i915, e->class));
+
+ result = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+
+ for (int n = 2; n <= 16; n <<= 1) {
+ int timeline = sw_sync_timeline_create();
+ int nframes = timeout * NSEC_PER_SEC / frame_ns + 1;
+ const int nchild = n - 1; /* odd for easy medians */
+ const int lo = nchild / 4;
+ const int hi = (3 * nchild + 3) / 4 - 1;
+ struct igt_mean m;
+
+ memset(result, 0, (nchild + 1) * 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, timeline, flags,
+ &result[nchild],
+ &result[child]);
+
+ gem_context_destroy(i915, ctx);
+ }
+
+ while (nframes--) {
+ struct timespec tv = { .tv_nsec = frame_ns };
+ nanosleep(&tv, NULL);
+ sw_sync_timeline_inc(timeline, 1);
+ }
+ result[nchild] = 1;
+ for (int child = 0; child < nchild; child++) {
+ while (!READ_ONCE(result[child])) {
+ struct timespec tv = { .tv_nsec = frame_ns };
+ nanosleep(&tv, NULL);
+ sw_sync_timeline_inc(timeline, 1);
+ }
+ }
+ igt_waitchildren();
+ close(timeline);
+
+ igt_mean_init(&m);
+ for (int child = 0; child < nchild; child++)
+ igt_mean_add(&m, result[child]);
+
+ qsort(result, nchild, sizeof(*result), cmp_ul);
+ igt_info("%d clients, range: [%.1f, %.1f], iqr: [%.1f, %.1f], median: %.1f, mean: %.1f ± %.2f ms\n",
+ nchild,
+ 1e-6 * result[0], 1e-6 * result[nchild - 1],
+ 1e-6 * result[lo], 1e-6 * result[hi],
+ 1e-6 * result[nchild / 2],
+ 1e-6 * igt_mean_get(&m),
+ 1e-6 * sqrt(igt_mean_get_variance(&m)));
+
+#if 0
+ /* Mean within 10% of target */
+ igt_assert( 9 * igt_mean_get(&m) > 10 * frame_ns &&
+ 10 * igt_mean_get(&m) < 9 * frame_ns);
+
+ /* Variance [inter-quartile range] is less than 33% of median */
+ igt_assert(3 * result[hi] - result[lo] < result[nchild / 2]);
+#endif
+ }
+
+ 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 +3000,13 @@ igt_main
test_each_engine_store("promotion", fd, e)
promotion(fd, e->flags);
+ test_each_engine_store("fair-none", fd, e)
+ fairness(fd, e, 2, 0);
+ test_each_engine_store("fair-pace", fd, e)
+ fairness(fd, e, 2, F_PACING);
+ test_each_engine_store("fair-sync", fd, e)
+ fairness(fd, e, 2, F_PACING | F_EXTERNAL);
+
igt_subtest_group {
igt_fixture {
igt_require(gem_scheduler_has_preemption(fd));
--
2.27.0.rc2
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