igt/gem_sync: Show the baseline poll latency for wakeups

Distinguish between the latency required to switch away from the
pollable spinner into the target nops from the client wakeup of
synchronisation on the last nop.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

1 files changed, 31 insertions, 4 deletions

diff --git a/tests/gem_sync.c b/tests/gem_sync.c
index 60d61a02..493ae61d 100644
--- a/tests/gem_sync.c
+++ b/tests/gem_sync.c
@@ -207,7 +207,7 @@ wakeup_ring(int fd, unsigned ring, int timeout, int wlen)
 		const uint32_t bbe = MI_BATCH_BUFFER_END;
 		struct drm_i915_gem_exec_object2 object;
 		struct drm_i915_gem_execbuffer2 execbuf;
-		double end, this, elapsed, now;
+		double end, this, elapsed, now, baseline;
 		unsigned long cycles;
 		uint32_t cmd;
 		igt_spin_t *spin;
@@ -233,6 +233,32 @@ wakeup_ring(int fd, unsigned ring, int timeout, int wlen)
 		igt_spin_batch_end(spin);
 		gem_sync(fd, object.handle);
 
+		for (int warmup = 0; warmup <= 1; warmup++) {
+			end = gettime() + timeout/10.;
+			elapsed = 0;
+			cycles = 0;
+			do {
+				*spin->batch = cmd;
+				*spin->running = 0;
+				gem_execbuf(fd, &spin->execbuf);
+				while (!READ_ONCE(*spin->running))
+					;
+
+				this = gettime();
+				igt_spin_batch_end(spin);
+				gem_sync(fd, spin->handle);
+				now = gettime();
+
+				elapsed += now - this;
+				cycles++;
+			} while (now < end);
+			baseline = elapsed / cycles;
+		}
+		igt_info("%s%saseline %ld cycles: %.3f us\n",
+			 names[child % num_engines] ?: "",
+			 names[child % num_engines] ? " b" : "B",
+			 cycles, elapsed*1e6/cycles);
+
 		end = gettime() + timeout;
 		elapsed = 0;
 		cycles = 0;
@@ -254,16 +280,17 @@ wakeup_ring(int fd, unsigned ring, int timeout, int wlen)
 			elapsed += now - this;
 			cycles++;
 		} while (now < end);
+		elapsed -= cycles * baseline;
 
-		igt_info("%s%sompleted %ld cycles: %.3f us\n",
+		igt_info("%s%sompleted %ld cycles: %.3f + %.3f us\n",
 			 names[child % num_engines] ?: "",
 			 names[child % num_engines] ? " c" : "C",
-			 cycles, elapsed*1e6/cycles);
+			 cycles, 1e6*baseline, elapsed*1e6/cycles);
 
 		igt_spin_batch_free(fd, spin);
 		gem_close(fd, object.handle);
 	}
-	igt_waitchildren_timeout(timeout+10, NULL);
+	igt_waitchildren_timeout(2*timeout, NULL);
 	igt_assert_eq(intel_detect_and_clear_missed_interrupts(fd), 0);
 }