[igt-dev] [PATCH i-g-t] i915/gem_exec_fair: Try to spot unfairness
Chris Wilson
chris at chris-wilson.co.uk
Mon Dec 21 11:58:55 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.
v2: igt_assert_f and more commentary; exclude vip from client stats,
include range of frame intervals from each individual client
v3: Write down what the test actually does!
v4: Split out to gem_exec_fair so that we can apply CI filtering to
reduce the test set
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/Makefile.sources | 3 +
tests/i915/gem_exec_fair.c | 914 +++++++++++++++++++++++++++++++++++
tests/intel-ci/blacklist.txt | 1 +
tests/meson.build | 1 +
4 files changed, 919 insertions(+)
create mode 100644 tests/i915/gem_exec_fair.c
diff --git a/tests/Makefile.sources b/tests/Makefile.sources
index d9c8f6104..db2be6a17 100644
--- a/tests/Makefile.sources
+++ b/tests/Makefile.sources
@@ -275,6 +275,9 @@ gem_exec_reloc_SOURCES = i915/gem_exec_reloc.c
TESTS_progs += gem_exec_schedule
gem_exec_schedule_SOURCES = i915/gem_exec_schedule.c
+TESTS_progs += gem_exec_fair
+gem_exec_fair_SOURCES = i915/gem_exec_fair.c
+
TESTS_progs += gem_exec_store
gem_exec_store_SOURCES = i915/gem_exec_store.c
diff --git a/tests/i915/gem_exec_fair.c b/tests/i915/gem_exec_fair.c
new file mode 100644
index 000000000..76bf0f461
--- /dev/null
+++ b/tests/i915/gem_exec_fair.c
@@ -0,0 +1,914 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2016 Intel Corporation
+ */
+
+#include "config.h"
+
+#include <pthread.h>
+#include <sys/poll.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/syscall.h>
+#include <sched.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "i915/gem.h"
+#include "i915/gem_ring.h"
+#include "igt.h"
+#include "igt_rand.h"
+#include "igt_rapl.h"
+#include "igt_sysfs.h"
+#include "igt_vgem.h"
+#include "sw_sync.h"
+
+IGT_TEST_DESCRIPTION("Check that GPU time and execution order is fairly distributed across clients");
+
+static unsigned int offset_in_page(void *addr)
+{
+ return (uintptr_t)addr & 4095;
+}
+
+static uint32_t __batch_create(int i915, uint32_t offset)
+{
+ const uint32_t bbe = MI_BATCH_BUFFER_END;
+ uint32_t handle;
+
+ handle = gem_create(i915, ALIGN(offset + 4, 4096));
+ gem_write(i915, handle, offset, &bbe, sizeof(bbe));
+
+ return handle;
+}
+
+static uint32_t batch_create(int i915)
+{
+ return __batch_create(i915, 0);
+}
+
+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_ctx_ticks(int i915, uint64_t ns)
+{
+ int f = read_timestamp_frequency(i915);
+ if (intel_gen(intel_get_drm_devid(i915)) == 11)
+ f = 12500000; /* icl!!! are you feeling alright? CTX vs CS */
+ return div64_u64_round_up(ns * f, 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 RUNTIME (base + 0x3a8)
+ enum { START_TS, NOW_TS };
+ uint32_t *map, *cs, *jmp;
+
+ igt_require(base);
+
+ /* Loop until CTX_TIMESTAMP - initial > @ns */
+
+ 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++ = RUNTIME;
+ *cs++ = CS_GPR(START_TS);
+
+ while (offset_in_page(cs) & 63)
+ *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++ = RUNTIME;
+ *cs++ = CS_GPR(NOW_TS);
+
+ /* delta = now - start; inverted to match COND_BBE */
+ *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);
+
+ /* Save delta for reading by COND_BBE */
+ *cs++ = 0x24 << 23 | (1 + use_64b); /* SRM */
+ *cs++ = CS_GPR(NOW_TS);
+ *cs++ = addr + 4000;
+ *cs++ = addr >> 32;
+
+ /* Delay between SRM and COND_BBE to post the writes */
+ for (int n = 0; n < 8; n++) {
+ *cs++ = MI_STORE_DWORD_IMM;
+ if (use_64b) {
+ *cs++ = addr + 4064;
+ *cs++ = addr >> 32;
+ } else {
+ *cs++ = 0;
+ *cs++ = addr + 4064;
+ }
+ *cs++ = 0;
+ }
+
+ /* Break if delta [time elapsed] > ns */
+ *cs++ = MI_COND_BATCH_BUFFER_END | MI_DO_COMPARE | (1 + use_64b);
+ *cs++ = ~ns_to_ctx_ticks(i915, ns);
+ *cs++ = addr + 4000;
+ *cs++ = addr >> 32;
+
+ /* Otherwise back to recalculating delta */
+ *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,
+ };
+
+ obj.offset = obj.handle << 12;
+ 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 { INC, 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;
+
+ /* Record the current CS_TIMESTAMP into a journal [a 512 slot ring]. */
+ *cs++ = 0x24 << 23 | (1 + use_64b); /* SRM */
+ *cs++ = CS_TIMESTAMP;
+ timestamp_lo = cs;
+ *cs++ = addr;
+ *cs++ = addr >> 32;
+
+ /* Load the address + inc & mask variables */
+ *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(INC);
+ *cs++ = 4;
+ *cs++ = MI_LOAD_REGISTER_IMM;
+ *cs++ = CS_GPR(INC) + 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;
+
+ /* Increment the [ring] address for saving CS_TIMESTAMP */
+ *cs++ = MI_MATH(8);
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCA, MI_MATH_REG(INC));
+ *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);
+
+ /* Rewrite the batch buffer for the next execution */
+ *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,
+ };
+
+ obj.offset = obj.handle << 12;
+ 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 uint32_t *a = A, *b = B;
+
+ if (*a < *b)
+ return -1;
+ else if (*a > *b)
+ return 1;
+ else
+ return 0;
+}
+
+static bool has_ctx_timestamp(int i915, const struct intel_execution_engine2 *e)
+{
+ const int gen = intel_gen(intel_get_drm_devid(i915));
+
+ if (gen == 8 && e->class == I915_ENGINE_CLASS_VIDEO)
+ return false; /* looks fubar */
+
+ return true;
+}
+
+static struct intel_execution_engine2
+pick_random_engine(int i915, const struct intel_execution_engine2 *not)
+{
+ const struct intel_execution_engine2 *e;
+ unsigned int count = 0;
+
+ __for_each_physical_engine(i915, e) {
+ if (e->flags == not->flags)
+ continue;
+ if (!gem_class_has_mutable_submission(i915, e->class))
+ continue;
+ count++;
+ }
+ if (!count)
+ return *not;
+
+ count = rand() % count;
+ __for_each_physical_engine(i915, e) {
+ if (e->flags == not->flags)
+ continue;
+ if (!gem_class_has_mutable_submission(i915, e->class))
+ continue;
+ if (!count--)
+ break;
+ }
+
+ return *e;
+}
+
+static void fair_child(int i915, uint32_t ctx,
+ const struct intel_execution_engine2 *e,
+ uint64_t frame_ns,
+ int timeline,
+ uint32_t common,
+ unsigned int flags,
+ unsigned long *ctl,
+ unsigned long *median,
+ unsigned long *iqr)
+#define F_SYNC (1 << 0)
+#define F_PACE (1 << 1)
+#define F_FLOW (1 << 2)
+#define F_HALF (1 << 3)
+#define F_SOLO (1 << 4)
+#define F_SPARE (1 << 5)
+#define F_NEXT (1 << 6)
+#define F_VIP (1 << 7)
+#define F_RRUL (1 << 8)
+#define F_SHARE (1 << 9)
+#define F_PING (1 << 10)
+#define F_THROTTLE (1 << 11)
+#define F_ISOLATE (1 << 12)
+{
+ const int batches_per_frame = flags & F_SOLO ? 1 : 3;
+ struct drm_i915_gem_exec_object2 obj[4] = {
+ {},
+ {
+ .handle = common ?: gem_create(i915, 4096),
+ },
+ delay_create(i915, ctx, e, frame_ns / batches_per_frame),
+ delay_create(i915, ctx, e, frame_ns / batches_per_frame),
+ };
+ struct intel_execution_engine2 ping = *e;
+ int p_fence = -1, n_fence = -1;
+ unsigned long count = 0;
+ int n;
+
+ srandom(getpid());
+ if (flags & F_PING)
+ ping = pick_random_engine(i915, e);
+ obj[0] = tslog_create(i915, ctx, &ping);
+
+ while (!READ_ONCE(*ctl)) {
+ struct drm_i915_gem_execbuffer2 execbuf = {
+ .buffers_ptr = to_user_pointer(obj),
+ .buffer_count = 3,
+ .rsvd1 = ctx,
+ .rsvd2 = -1,
+ .flags = e->flags,
+ };
+
+ if (flags & F_FLOW) {
+ unsigned int seq;
+
+ seq = count;
+ if (flags & F_NEXT)
+ seq++;
+
+ execbuf.rsvd2 =
+ sw_sync_timeline_create_fence(timeline, seq);
+ 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);
+ close(execbuf.rsvd2);
+
+ execbuf.buffer_count = 1;
+ execbuf.batch_start_offset = 2048;
+ execbuf.flags = ping.flags | I915_EXEC_FENCE_IN;
+ execbuf.rsvd2 = n_fence;
+ gem_execbuf(i915, &execbuf);
+
+ if (flags & F_PACE && p_fence != -1) {
+ struct pollfd pfd = {
+ .fd = p_fence,
+ .events = POLLIN,
+ };
+ poll(&pfd, 1, -1);
+ }
+ close(p_fence);
+
+ if (flags & F_SYNC) {
+ struct pollfd pfd = {
+ .fd = n_fence,
+ .events = POLLIN,
+ };
+ poll(&pfd, 1, -1);
+ }
+
+ if (flags & F_THROTTLE)
+ igt_ioctl(i915, DRM_IOCTL_I915_GEM_THROTTLE, 0);
+
+ igt_swap(obj[2], obj[3]);
+ igt_swap(p_fence, n_fence);
+ count++;
+ }
+ close(p_fence);
+
+ gem_close(i915, obj[3].handle);
+ gem_close(i915, obj[2].handle);
+ if (obj[1].handle != common)
+ gem_close(i915, obj[1].handle);
+
+ gem_sync(i915, obj[0].handle);
+ if (median) {
+ uint32_t *map;
+
+ /*
+ * We recorded the CS_TIMESTAMP of each frame, and if
+ * the GPU is being shared completely fairly, we expect
+ * each frame to be at the same interval from the last.
+ *
+ * Compute the interval between frames and report back
+ * both the median interval and the range for this client.
+ */
+
+ map = gem_mmap__device_coherent(i915, obj[0].handle,
+ 0, 4096, PROT_WRITE);
+ for (n = 1; n < min(count, 512); n++) {
+ igt_assert(map[n]);
+ map[n - 1] = map[n] - map[n - 1];
+ }
+ qsort(map, --n, sizeof(*map), cmp_u32);
+ *iqr = ticks_to_ns(i915, map[(3 * n + 3) / 4] - map[n / 4]);
+ *median = ticks_to_ns(i915, map[n / 2]);
+ munmap(map, 4096);
+ }
+ gem_close(i915, obj[0].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 uint64_t d_cpu_time(const struct rusage *a, const struct rusage *b)
+{
+ uint64_t cpu_time = 0;
+
+ cpu_time += (a->ru_utime.tv_sec - b->ru_utime.tv_sec) * NSEC_PER_SEC;
+ cpu_time += (a->ru_utime.tv_usec - b->ru_utime.tv_usec) * 1000;
+
+ cpu_time += (a->ru_stime.tv_sec - b->ru_stime.tv_sec) * NSEC_PER_SEC;
+ cpu_time += (a->ru_stime.tv_usec - b->ru_stime.tv_usec) * 1000;
+
+ return cpu_time;
+}
+
+static void timeline_advance(int timeline, int delay_ns)
+{
+ struct timespec tv = { .tv_nsec = delay_ns };
+ nanosleep(&tv, NULL);
+ sw_sync_timeline_inc(timeline, 1);
+}
+
+static void fairness(int i915,
+ const struct intel_execution_engine2 *e,
+ int timeout, unsigned int flags)
+{
+ const int frame_ns = 16666 * 1000;
+ const int fence_ns = flags & F_HALF ? 2 * frame_ns : frame_ns;
+ unsigned long *result, *iqr;
+ uint32_t common = 0;
+
+ igt_require(has_ctx_timestamp(i915, e));
+ igt_require(gem_class_has_mutable_submission(i915, e->class));
+
+ if (flags & F_SHARE)
+ common = gem_create(i915, 4095);
+
+ result = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+ igt_assert(result != MAP_FAILED);
+ iqr = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+ igt_assert(iqr != MAP_FAILED);
+
+ /*
+ * The combined workload always runs at a 60fps target (unless F_HALF!).
+ * This gives a frame of interval of 16ms that is evenly split across
+ * all the clients, so simulating a system with a bunch of clients that
+ * are perfectly balanced and can sustain 60fps. Our job is to ensure
+ * that each client does run at a smooth 60fps.
+ *
+ * Each client runs a fixed length delay loop (as a single request,
+ * or split into 3) and then records the CS_TIMESTAMP after completing
+ * its delay. Given a fair allotment of GPU time to each client,
+ * that timestamp will [ideally] be at a precise 16ms intervals.
+ * In practice, time is wasted on context switches, so as the number
+ * of clients increases, the proprotion of time spent on context
+ * switches grows. As we get to 64 render clients, we will be spending
+ * as much time in context switches as executing the client workloads.
+ *
+ * Each client frame may be paced by some throttling technique found
+ * in the wild. i.e. each client may wait until a simulated vblank
+ * to indicate the start of a new frame, or it may wait until the
+ * completion of a previous frame. This causes submission from each
+ * client and across the system to be chunky and uneven.
+ *
+ * We look at the variation of frame intervals within each client, and
+ * the variation of the medians across the clients to see if the
+ * distribution (budget) of GPU time was fair enough.
+ *
+ * Alternative (and important) metrics will be more latency centric;
+ * looking at how well we can sustain meeting deadline given competition
+ * by clients for the GPU.
+ */
+
+ for (int n = 2; n <= 256; n <<= 1) { /* 32 == 500us per client */
+ int timeline = sw_sync_timeline_create();
+ int nfences = timeout * NSEC_PER_SEC / fence_ns + 1;
+ int nchild = n - 1; /* odd for easy medians */
+ const int child_ns = frame_ns / (nchild + !!(flags & F_SPARE));
+ const int lo = nchild / 4;
+ const int hi = (3 * nchild + 3) / 4 - 1;
+ struct rusage old_usage, usage;
+ uint64_t cpu_time, d_time;
+ struct timespec tv;
+ struct igt_mean m;
+
+ memset(result, 0, (nchild + 1) * sizeof(result[0]));
+
+ if (flags & F_PING) { /* fill the others with light bg load */
+ struct intel_execution_engine2 *ping;
+
+ __for_each_physical_engine(i915, ping) {
+ if (ping->flags == e->flags)
+ continue;
+
+ igt_fork(child, 1) {
+ uint32_t ctx = gem_context_clone_with_engines(i915, 0);
+
+ fair_child(i915, ctx, ping,
+ child_ns / 8,
+ -1, common,
+ F_SOLO | F_PACE | F_SHARE,
+ &result[nchild],
+ NULL, NULL);
+
+ gem_context_destroy(i915, ctx);
+ }
+ }
+ }
+
+ getrusage(RUSAGE_CHILDREN, &old_usage);
+ igt_nsec_elapsed(memset(&tv, 0, sizeof(tv)));
+ igt_fork(child, nchild) {
+ uint32_t ctx;
+
+ if (flags & F_ISOLATE) {
+ int clone, dmabuf = -1;
+
+ if (common)
+ dmabuf = prime_handle_to_fd(i915, common);
+
+ clone = gem_reopen_driver(i915);
+ gem_context_copy_engines(i915, 0, clone, 0);
+ i915 = clone;
+
+ if (dmabuf != -1)
+ common = prime_fd_to_handle(i915, dmabuf);
+ }
+
+ ctx = gem_context_clone_with_engines(i915, 0);
+
+ if (flags & F_VIP && child == 0) {
+ gem_context_set_priority(i915, ctx, 1023);
+ flags |= F_FLOW;
+ }
+ if (flags & F_RRUL && child == 0)
+ flags |= F_SOLO | F_FLOW | F_SYNC;
+
+ fair_child(i915, ctx, e, child_ns,
+ timeline, common, flags,
+ &result[nchild],
+ &result[child], &iqr[child]);
+
+ gem_context_destroy(i915, ctx);
+ }
+
+ while (nfences--)
+ timeline_advance(timeline, fence_ns);
+
+ result[nchild] = 1;
+ for (int child = 0; child < nchild; child++) {
+ while (!READ_ONCE(result[child]))
+ timeline_advance(timeline, fence_ns);
+ }
+
+ igt_waitchildren();
+ close(timeline);
+
+ /*
+ * Are we running out of CPU time, and fail to submit frames?
+ *
+ * We try to rule out any undue impact on the GPU scheduling
+ * from the CPU scheduler by looking for core saturation. If
+ * we may be in a situation where the clients + kernel are
+ * taking a whole core (think lockdep), then it is increasingly
+ * likely that our measurements include delays from the CPU
+ * scheduler. Err on the side of caution.
+ */
+ d_time = igt_nsec_elapsed(&tv);
+ getrusage(RUSAGE_CHILDREN, &usage);
+ cpu_time = d_cpu_time(&usage, &old_usage);
+ igt_debug("CPU usage: %.0f%%\n", 100. * cpu_time / d_time);
+ if (4 * cpu_time > 3 * d_time) {
+ if (nchild > 7) /* good enough to judge pass/fail */
+ break;
+
+ igt_skip_on_f(4 * cpu_time > 3 * d_time,
+ "%.0f%% CPU usage, presuming capacity exceeded\n",
+ 100. * cpu_time / d_time);
+ }
+
+ /* With no contention, we should match our target frametime */
+ if (nchild == 1) {
+ igt_assert(4 * result[0] > 3 * fence_ns &&
+ 3 * result[0] < 4 * fence_ns);
+ continue;
+ }
+
+ /*
+ * The VIP should always be able to hit the target frame rate;
+ * regardless of budget contention from lessor clients.
+ */
+ if (flags & (F_VIP | F_RRUL)) {
+ igt_info("VIP interval %.2fms, range %.2fms\n",
+ 1e-6 * result[0], 1e-6 * iqr[0]);
+ igt_assert_f(4 * result[0] > 3 * fence_ns &&
+ 3 * result[0] < 4 * fence_ns,
+ "VIP expects to run exactly when it wants, expects an interval of %.2fms, was %.2fms\n",
+ 1e-6 * fence_ns, 1e-6 * result[0]);
+ igt_assert_f(2 * iqr[0] < result[0],
+ "VIP frame IQR %.2fms exceeded median threshold %.2fms\n",
+ 1e-6 * iqr[0],
+ 1e-6 * result[0] / 2);
+ if (!--nchild)
+ continue;
+
+ /* Exclude the VIP result from the plebian statistics */
+ memmove(result, result + 1, nchild * sizeof(*result));
+ memmove(iqr, iqr + 1, nchild * sizeof(*iqr));
+ }
+
+ igt_mean_init(&m);
+ for (int child = 0; child < nchild; child++)
+ igt_mean_add(&m, result[child]);
+
+ qsort(result, nchild, sizeof(*result), cmp_ul);
+ qsort(iqr, nchild, sizeof(*iqr), cmp_ul);
+
+ /*
+ * The target interval for median/mean is 16ms (fence_ns).
+ * However, this work is evenly split across the clients so
+ * the range (and median) of client medians may be much less
+ * than 16ms [16/3N]. We present median of medians to try
+ * and avoid any instability while running in CI; at the cost
+ * of insensitivity!
+ */
+ igt_info("%3d clients, range: [%.1f, %.1f], iqr: [%.1f, %.1f], median: %.1f [%.1f, %.1f], mean: %.1f ± %.2f ms, cpu: %.0f%%\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 * iqr[lo], 1e-6 * iqr[hi],
+ 1e-6 * igt_mean_get(&m),
+ 1e-6 * sqrt(igt_mean_get_variance(&m)),
+ 100. * cpu_time / d_time);
+
+ igt_assert_f(iqr[nchild / 2] < 2 * result[nchild / 2],
+ "Child frame IQR %.2fms exceeded median threshold %.2fms\n",
+ 1e-6 * iqr[nchild / 2],
+ 1e-6 * result[nchild / 2] * 2);
+
+ igt_assert_f(4 * igt_mean_get(&m) > 3 * result[nchild / 2] &&
+ 3 * igt_mean_get(&m) < 4 * result[nchild / 2],
+ "Mean of client interval %.2fms differs from median %.2fms, distribution is skewed\n",
+
+ 1e-6 * igt_mean_get(&m), 1e-6 * result[nchild / 2]);
+
+ igt_assert_f(result[nchild / 2] > frame_ns / 2,
+ "Median client interval %.2fms did not match target interval %.2fms\n",
+ 1e-6 * result[nchild / 2], 1e-6 * frame_ns);
+
+
+ igt_assert_f(result[hi] - result[lo] < result[nchild / 2],
+ "Interquartile range of client intervals %.2fms is as large as the median threshold %.2fms, clients are not evenly distributed!\n",
+ 1e-6 * (result[hi] - result[lo]),
+ 1e-6 * result[nchild / 2]);
+
+ /* May be slowed due to sheer volume of context switches */
+ if (result[0] > 2 * fence_ns)
+ break;
+ }
+
+ munmap(iqr, 4096);
+ munmap(result, 4096);
+ if (common)
+ gem_close(i915, common);
+}
+
+igt_main
+{
+ static const struct {
+ const char *name;
+ unsigned int flags;
+ unsigned int basic;
+#define BASIC (1 << 0)
+#define BASIC_ALL (1 << 1)
+ } fair[] = {
+ /*
+ * none - maximal greed in each client
+ *
+ * Push as many frames from each client as fast as possible
+ */
+ { "none", 0, BASIC_ALL },
+ { "none-vip", F_VIP, BASIC }, /* one vip client must meet deadlines */
+ { "none-solo", F_SOLO, BASIC }, /* 1 batch per frame per client */
+ { "none-share", F_SHARE, BASIC }, /* read from a common buffer */
+ { "none-rrul", F_RRUL, BASIC }, /* "realtime-response under load" */
+ { "none-ping", F_PING }, /* measure inter-engine fairness */
+
+ /*
+ * throttle - original per client throttling
+ *
+ * Used for front buffering rendering where there is no
+ * extenal frame marker. Each client tries to only keep
+ * 20ms of work submitted, though that measurement is
+ * flawed...
+ *
+ * This is used by Xorg to try and maintain some resembalance
+ * of input/output consistency when being feed a continuous
+ * stream of X11 draw requests straight into scanout, where
+ * the clients may submit the work faster than can be drawn.
+ *
+ * Throttling tracks requests per-file (and assumes that
+ * all requests are in submission order across the whole file),
+ * so we split each child to its own fd.
+ */
+ { "throttle", F_THROTTLE | F_ISOLATE, BASIC },
+ { "throttle-vip", F_THROTTLE | F_ISOLATE | F_VIP },
+ { "throttle-solo", F_THROTTLE | F_ISOLATE | F_SOLO },
+ { "throttle-share", F_THROTTLE | F_ISOLATE | F_SHARE },
+ { "throttle-rrul", F_THROTTLE | F_ISOLATE | F_RRUL },
+
+ /*
+ * pace - mesa "submit double buffering"
+ *
+ * Submit a frame, wait for previous frame to start. This
+ * prevents each client from getting too far ahead of its
+ * rendering, maintaining a consistent input/output latency.
+ */
+ { "pace", F_PACE, BASIC_ALL },
+ { "pace-solo", F_PACE | F_SOLO, BASIC },
+ { "pace-share", F_PACE | F_SOLO | F_SHARE, BASIC },
+ { "pace-ping", F_PACE | F_SOLO | F_SHARE | F_PING},
+
+ /* sync - only submit a frame at a time */
+ { "sync", F_SYNC, BASIC },
+ { "sync-vip", F_SYNC | F_VIP },
+ { "sync-solo", F_SYNC | F_SOLO },
+
+ /* flow - synchronise execution against the clock (vblank) */
+ { "flow", F_PACE | F_FLOW, BASIC },
+ { "flow-solo", F_PACE | F_FLOW | F_SOLO },
+ { "flow-share", F_PACE | F_FLOW | F_SHARE },
+ { "flow-ping", F_PACE | F_FLOW | F_SHARE | F_PING },
+
+ /* next - submit ahead of the clock (vblank double buffering) */
+ { "next", F_PACE | F_FLOW | F_NEXT },
+ { "next-solo", F_PACE | F_FLOW | F_NEXT | F_SOLO },
+ { "next-share", F_PACE | F_FLOW | F_NEXT | F_SHARE },
+ { "next-ping", F_PACE | F_FLOW | F_NEXT | F_SHARE | F_PING },
+
+ /* spare - underutilise by a single client timeslice */
+ { "spare", F_PACE | F_FLOW | F_SPARE },
+ { "spare-solo", F_PACE | F_FLOW | F_SPARE | F_SOLO },
+
+ /* half - run at half pace (submit 16ms of work every 32ms) */
+ { "half", F_PACE | F_FLOW | F_HALF },
+ { "half-solo", F_PACE | F_FLOW | F_HALF | F_SOLO },
+
+ {}
+ };
+ const struct intel_execution_engine2 *e;
+ int i915 = -1;
+
+ igt_fixture {
+ igt_require_sw_sync();
+
+ i915 = drm_open_driver_master(DRIVER_INTEL);
+ gem_submission_print_method(i915);
+ gem_scheduler_print_capability(i915);
+
+ igt_require_gem(i915);
+ gem_require_mmap_wc(i915);
+ gem_require_contexts(i915);
+ igt_require(gem_scheduler_enabled(i915));
+ igt_require(gem_scheduler_has_ctx_priority(i915));
+
+ igt_info("CS timestamp frequency: %d\n",
+ read_timestamp_frequency(i915));
+ igt_require(intel_gen(intel_get_drm_devid(i915)) >= 8);
+
+ igt_fork_hang_detector(i915);
+ }
+
+ /* First we do a trimmed set of basic tests for faster CI */
+ for (typeof(*fair) *f = fair; f->name; f++) {
+ if (!f->basic)
+ continue;
+
+ igt_subtest_with_dynamic_f("basic-%s", f->name) {
+ __for_each_physical_engine(i915, e) {
+ if (!gem_class_can_store_dword(i915, e->class))
+ continue;
+
+ if (e->flags && !(f->basic & BASIC_ALL))
+ continue;
+
+ igt_dynamic_f("%s", e->name)
+ fairness(i915, e, 1, f->flags);
+ }
+ }
+ }
+
+ for (typeof(*fair) *f = fair; f->name; f++) {
+ igt_subtest_with_dynamic_f("fair-%s", f->name) {
+ __for_each_physical_engine(i915, e) {
+ if (!gem_class_can_store_dword(i915, e->class))
+ continue;
+
+ igt_dynamic_f("%s", e->name)
+ fairness(i915, e, 5, f->flags);
+ }
+ }
+ }
+
+ igt_fixture {
+ igt_stop_hang_detector();
+ close(i915);
+ }
+}
diff --git a/tests/intel-ci/blacklist.txt b/tests/intel-ci/blacklist.txt
index c6af22b30..6716cc97f 100644
--- a/tests/intel-ci/blacklist.txt
+++ b/tests/intel-ci/blacklist.txt
@@ -26,6 +26,7 @@ igt at gem_evict_alignment(@.*)?
igt at gem_evict_everything(@.*)?
igt at gem_exec_big@(?!.*single).*
igt at gem_exec_capture@many-(?!4K-).*
+igt at gem_exec_fair@(?!.*basic).*
igt at gem_exec_fence@.*hang.*
igt at gem_exec_flush@(?!.*basic).*
igt at gem_exec_latency(@.*)?
diff --git a/tests/meson.build b/tests/meson.build
index 9d6006709..cd3427485 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -148,6 +148,7 @@ i915_progs = [
'gem_exec_capture',
'gem_exec_create',
'gem_exec_endless',
+ 'gem_exec_fair',
'gem_exec_fence',
'gem_exec_flush',
'gem_exec_gttfill',
--
2.29.2
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