From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
We want to make sure RT tasks which use a lot of CPU times can submit
batch buffers with roughly the same latency (and certainly not worse)
compared to normal tasks.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
tests/gem_exec_latency.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 176 insertions(+)
diff --git a/tests/gem_exec_latency.c b/tests/gem_exec_latency.c
index 9498c0921e60..420ede0f83a0 100644
--- a/tests/gem_exec_latency.c
+++ b/tests/gem_exec_latency.c
@@ -36,11 +36,15 @@
#include <sys/time.h>
#include <sys/signal.h>
#include <time.h>
+#include <sched.h>
#include "drm.h"
#include "igt_sysfs.h"
#include "igt_vgem.h"
+#include "igt_dummyload.h"
+#include "igt_stats.h"
+
#include "i915/gem_ring.h"
#define LOCAL_I915_EXEC_NO_RELOC (1<<11)
@@ -351,6 +355,172 @@ static void latency_from_ring(int fd,
}
}
+static void __rearm_spin_batch(igt_spin_t *spin)
+{
+ const uint32_t mi_arb_chk = 0x5 << 23;
+
+ *spin->batch = mi_arb_chk;
+ *spin->running = 0;
+ __sync_synchronize();
+}
+
+static void
+__submit_spin_batch(int fd, igt_spin_t *spin, unsigned int flags)
+{
+ struct drm_i915_gem_execbuffer2 eb = spin->execbuf;
+
+ eb.flags &= ~(0x3f | I915_EXEC_BSD_MASK);
+ eb.flags |= flags | I915_EXEC_NO_RELOC;
+
+ gem_execbuf(fd, &eb);
+}
+
+struct rt_pkt
+{
+#define RT_OK (0)
+#define RT_FAIL (1)
+#define RT_TIMEOUT (2)
+ int status;
+ struct igt_mean mean;
+ double max;
+};
+
+static void __spin_wait(struct rt_pkt *msg, igt_spin_t *spin, double *t_wait)
+{
+ struct timespec ts = { };
+ uint64_t t_last = 0;
+
+ igt_nsec_elapsed(&ts);
+
+ while (!READ_ONCE(*spin->running)) {
+ uint64_t t = igt_nsec_elapsed(&ts);
+
+ if ((t - t_last) > 5UL * NSEC_PER_SEC) {
+ /* Absolute timeout to save time. */
+ msg->status = RT_TIMEOUT;
+ } else if ((t - t_last) > NSEC_PER_SEC / 10) {
+ /* Backoff every 100ms to give it chance to complete. */
+ t_last = t;
+ usleep(1);
+ }
+ }
+
+ *t_wait = igt_nsec_elapsed(&ts) / 1e9;
+
+ msg->status = RT_OK;
+}
+
+/*
+ * Test whether RT thread which hogs the CPU a lot can submit work with
+ * reasonable latency.
+ */
+static void
+rthog_latency_on_ring(int fd, unsigned int ring, const char *name)
+{
+ const char *passname[] = { "warmup", "normal", "rt" };
+ struct rt_pkt res[3];
+ unsigned int i;
+ int link[2];
+ int ret;
+
+ igt_require(gem_can_store_dword(fd, ring));
+
+ igt_assert(pipe(link) == 0);
+
+ memset(res, 0, sizeof(res));
+
+ igt_fork(child, 1) {
+ unsigned int pass = 0; /* Three passes: warmup, normal, rt. */
+
+ do {
+ struct rt_pkt msg = { };
+ igt_spin_t *spin;
+
+ igt_mean_init(&msg.mean);
+
+ if (pass == 2) {
+ struct sched_param rt =
+ { .sched_priority = 99 };
+
+ ret = sched_setscheduler(0,
+ SCHED_FIFO | SCHED_RESET_ON_FORK,
+ &rt);
+ if (ret) {
+ igt_warn("Failed to set scheduling policy!\n");
+ msg.status = RT_FAIL;
+ write(link[1], &msg, sizeof(msg));
+ exit(1);
+ }
+ }
+
+ spin = __igt_spin_batch_new_poll(fd, 0, ring);
+ if (!spin) {
+ igt_warn("Failed to create spinner! (%s)\n",
+ passname[pass]);
+ msg.status = RT_FAIL;
+ write(link[1], &msg, sizeof(msg));
+ exit(1);
+ }
+ igt_spin_busywait_until_running(spin);
+
+ igt_until_timeout(pass > 0 ? 5 : 2) {
+ double t;
+
+ igt_spin_batch_end(spin);
+ gem_sync(fd, spin->handle);
+
+ __rearm_spin_batch(spin);
+ __submit_spin_batch(fd, spin, ring);
+
+ __spin_wait(&msg, spin, &t);
+ if (msg.status != RT_OK) {
+ igt_warn("Wait timeout! (%s)\n",
+ passname[pass]);
+ write(link[1], &msg, sizeof(msg));
+ exit(1);
+ }
+
+ if (t > msg.max)
+ msg.max = t;
+
+ igt_mean_add(&msg.mean, t);
+ }
+
+ igt_spin_batch_free(fd, spin);
+
+ igt_info("%10s: mean=%.2fus variance=%.2fus max=%.2fus (n=%lu)\n",
+ passname[pass],
+ igt_mean_get(&msg.mean) * 1e6,
+ igt_mean_get_variance(&msg.mean) * 1e6,
+ msg.max * 1e6,
+ msg.mean.count);
+
+ write(link[1], &msg, sizeof(msg));
+ } while (++pass < 3);
+
+ exit(0);
+ }
+
+ for (i = 0; i < 3; i++) {
+ ret = read(link[0], &res[i], sizeof(res[0]));
+ igt_assert_eq(ret, sizeof(res[0]));
+
+ igt_assert_eq(res[i].status, RT_OK);
+ }
+
+ close(link[0]);
+ close(link[1]);
+
+ igt_waitchildren();
+
+ /*
+ * Check that the submission latency variance for a task with RT
+ * priority is no larger than three times the same of a normal task.
+ */
+ igt_assert(igt_mean_get_variance(&res[2].mean) <
+ igt_mean_get_variance(&res[1].mean) * 3);
+}
+
igt_main
{
const struct intel_execution_engine *e;
@@ -391,6 +561,12 @@ igt_main
e->exec_id | e->flags,
e->name, 0);
+ igt_subtest_f("%s-rthog-submit", e->name)
+ rthog_latency_on_ring(device,
+ e->exec_id |
+ e->flags,
+ e->name);
+
igt_subtest_f("%s-dispatch-queued", e->name)
latency_on_ring(device,
e->exec_id | e->flags,
--
2.14.1
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