[igt-dev] [PATCH i-g-t] lib/i915: Trim ring measurement by one

[Chris Wilson]

Be a little more conservative in our ring measurement and exclude one
batch to leave room in case our user needs to wrap (where a request will
be expanded to cover the unused space at the end of the ring).

References: https://bugs.freedesktop.org/show_bug.cgi?id=111374
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 lib/i915/gem_ring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/i915/gem_ring.c b/lib/i915/gem_ring.c
index fdb9fc1b1..bf7f439e1 100644
--- a/lib/i915/gem_ring.c
+++ b/lib/i915/gem_ring.c
@@ -103,7 +103,7 @@ __gem_measure_ring_inflight(int fd, unsigned int engine, enum measure_ring_flags
 	} while (1);
 
 	igt_assert_eq(__execbuf(fd, &execbuf), -EINTR);
-	igt_assert(count);
+	igt_assert(count > 1);
 
 	memset(&itv, 0, sizeof(itv));
 	setitimer(ITIMER_REAL, &itv, NULL);
@@ -118,7 +118,8 @@ __gem_measure_ring_inflight(int fd, unsigned int engine, enum measure_ring_flags
 
 	gem_quiescent_gpu(fd);
 
-	return count;
+	/* Be conservative in case we must wrap later */
+	return count - 1;
 }
 
 /**
-- 
2.23.0.rc1