Since we are system_highpri_wq, we expected the heartbeat to be
scheduled promptly. However, we see delays of over 10ms upsetting our
assertions. Accept this as inevitable and bump the minimum error
threshold to 20ms (from 6 jiffies).
<6> [616.784749] rcs0: Heartbeat delay: 3570us [2802, 9188]
<6> [616.807790] bcs0: Heartbeat delay: 2111us [745, 4372]
<6> [616.853776] vcs0: Heartbeat delay: 6485us [2424, 11637]
<3> [616.859296] vcs0: Heartbeat delay was 6485us, expected less than 6000us
<3> [616.860901] i915/intel_heartbeat_live_selftests: live_heartbeat_fast failed with error -22
v2: More context from CI.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
index b88aa35ad75b..223ab88f7e57 100644
--- a/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
@@ -197,6 +197,7 @@ static int cmp_u32(const void *_a, const void *_b)
static int __live_heartbeat_fast(struct intel_engine_cs *engine)
{
+ const unsigned int error_threshold = max(20000u, jiffies_to_usecs(6));
struct intel_context *ce;
struct i915_request *rq;
ktime_t t0, t1;
@@ -254,12 +255,18 @@ static int __live_heartbeat_fast(struct intel_engine_cs *engine)
times[0],
times[ARRAY_SIZE(times) - 1]);
- /* Min work delay is 2 * 2 (worst), +1 for scheduling, +1 for slack */
- if (times[ARRAY_SIZE(times) / 2] > jiffies_to_usecs(6)) {
+ /*
+ * Ideally, the upper bound on min work delay would be something like
+ * 2 * 2 (worst), +1 for scheduling, +1 for slack. In practice, we
+ * are, even with system_wq_highpri, at the mercy of the CPU scheduler
+ * and may be stuck behind some slow work for many millisecond. Such
+ * as our very own display workers.
+ */
+ if (times[ARRAY_SIZE(times) / 2] > error_threshold) {
pr_err("%s: Heartbeat delay was %uus, expected less than %dus\n",
engine->name,
times[ARRAY_SIZE(times) / 2],
- jiffies_to_usecs(6));
+ error_threshold);
err = -EINVAL;
}
--
2.20.1
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