[igt-dev] [PATCH i-g-t 03/24] i915/gem_exec_schedule: Measure semaphore power consumption

Chris Wilson
2019-03-22T09:21:34Z

How much energy does spinning on a semaphore consume relative to plain
old spinning?

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
tests/i915/gem_exec_schedule.c | 72 +++++++++++++++++++++++++++++++++-
1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/tests/i915/gem_exec_schedule.c b/tests/i915/gem_exec_schedule.c
index a9383000a..4f0577b4e 100644
--- a/tests/i915/gem_exec_schedule.c
+++ b/tests/i915/gem_exec_schedule.c
@@ -29,9 +29,10 @@
#include <signal.h>

#include "igt.h"
-#include "igt_vgem.h"
+#include "igt_gpu_power.h"
#include "igt_rand.h"
#include "igt_sysfs.h"
+#include "igt_vgem.h"
#include "i915/gem_ring.h"

#define LO 0
@@ -1202,6 +1203,65 @@ static void test_pi_ringfull(int fd, unsigned int engine)
munmap(result, 4096);
}

+static void measure_semaphore_power(int i915)
+{
+ struct gpu_power power;
+ unsigned int engine, signaler;
+
+ igt_require(gpu_power_open(&power) == 0);
+
+ for_each_physical_engine(i915, signaler) {
+ struct gpu_power_sample s_spin[2];
+ struct gpu_power_sample s_sema[2];
+ double baseline, total;
+ int64_t jiffie = 1;
+ igt_spin_t *spin;
+
+ spin = __igt_spin_batch_new(i915,
+ .engine = signaler,
+ .flags = IGT_SPIN_POLL_RUN);
+ gem_wait(i915, spin->handle, &jiffie); /* waitboost */
+ igt_assert(spin->running);
+ igt_spin_busywait_until_running(spin);
+
+ gpu_power_read(&power, &s_spin[0]);
+ usleep(100*1000);
+ gpu_power_read(&power, &s_spin[1]);
+
+ /* Add a waiter to each engine */
+ for_each_physical_engine(i915, engine) {
+ igt_spin_t *sema;
+
+ if (engine == signaler)
+ continue;
+
+ sema = __igt_spin_batch_new(i915,
+ .engine = engine,
+ .dependency = spin->handle);
+
+ igt_spin_batch_free(i915, sema);
+ }
+ usleep(10); /* just give the tasklets a chance to run */
+
+ gpu_power_read(&power, &s_sema[0]);
+ usleep(100*1000);
+ gpu_power_read(&power, &s_sema[1]);
+
+ igt_spin_batch_free(i915, spin);
+
+ baseline = gpu_power_W(&power, &s_spin[0], &s_spin[1]);
+ total = gpu_power_W(&power, &s_sema[0], &s_sema[1]);
+
+ igt_info("%s: %.1fmW + %.1fmW (total %1.fmW)\n",
+ e__->name,
+ 1e3 * baseline,
+ 1e3 * (total - baseline),
+ 1e3 * total);
+ }
+
+ gpu_power_close(&power);
+}
+
igt_main
{
const struct intel_execution_engine *e;
@@ -1362,6 +1422,16 @@ igt_main
}
}

+ igt_subtest_group {
+ igt_fixture {
+ igt_require(gem_scheduler_enabled(fd));
+ igt_require(gem_scheduler_has_semaphores(fd));
+ }
+
+ igt_subtest("semaphore-power")
+ measure_semaphore_power(fd);
+ }
+
igt_fixture {
igt_stop_hang_detector();
close(fd);
--
2.20.1