From: John Harrison <John.C.Harrison@xxxxxxxxx>
Compute workloads are inherently not pre-emptible for long periods on
current hardware. As a workaround for this, the pre-emption timeout
for compute capable engines was disabled. This is undesirable with GuC
submission as it prevents per engine reset of hung contexts. Hence the
next patch will re-enable the timeout but bumped up by an order of
magnitude.
However, the heartbeat might not respect that. Depending upon current
activity, a pre-emption to the heartbeat pulse might not even be
attempted until the last heartbeat period. Which means that only one
period is granted for the pre-emption to occur. With the aforesaid
bump, the pre-emption timeout could be significantly larger than this
heartbeat period.
So adjust the heartbeat code to take the pre-emption timeout into
account. When it reaches the final (high priority) period, it now
ensures the delay before hitting reset is bigger than the pre-emption
timeout.
v2: Fix for selftests which adjust the heartbeat period manually.
v3: Add FIXME comment about selftests. Add extra FIXME comment and
drm_notices when setting heartbeat to a non-default value (review
feedback from Tvrtko)
Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
.../gpu/drm/i915/gt/intel_engine_heartbeat.c | 39 +++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index a3698f611f457..9a527e1f5be65 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -22,9 +22,37 @@
static bool next_heartbeat(struct intel_engine_cs *engine)
{
+ struct i915_request *rq;
long delay;
delay = READ_ONCE(engine->props.heartbeat_interval_ms);
+
+ rq = engine->heartbeat.systole;
+
+ /*
+ * FIXME: The final period extension is disabled if the period has been
+ * modified from the default. This is to prevent issues with certain
+ * selftests which override the value and expect specific behaviour.
+ * Once the selftests have been updated to either cope with variable
+ * heartbeat periods (or to override the pre-emption timeout as well,
+ * or just to add a selftest specific override of the extension), the
+ * generic override can be removed.
+ */
+ if (rq && rq->sched.attr.priority >= I915_PRIORITY_BARRIER &&
+ delay == engine->defaults.heartbeat_interval_ms) {
+ long longer;
+
+ /*
+ * The final try is at the highest priority possible. Up until now
+ * a pre-emption might not even have been attempted. So make sure
+ * this last attempt allows enough time for a pre-emption to occur.
+ */
+ longer = READ_ONCE(engine->props.preempt_timeout_ms) * 2;
+ longer = intel_clamp_heartbeat_interval_ms(engine, longer);
+ if (longer > delay)
+ delay = longer;
+ }
+
if (!delay)
return false;
@@ -288,6 +316,17 @@ int intel_engine_set_heartbeat(struct intel_engine_cs *engine,
if (!delay && !intel_engine_has_preempt_reset(engine))
return -ENODEV;
+ /* FIXME: Remove together with equally marked hack in next_heartbeat. */
+ if (delay != engine->defaults.heartbeat_interval_ms &&
+ delay < 2 * engine->props.preempt_timeout_ms) {
+ if (intel_engine_uses_guc(engine))
+ drm_notice(&engine->i915->drm, "%s heartbeat interval adjusted to a non-default value which may downgrade individual engine resets to full GPU resets!\n",
+ engine->name);
+ else
+ drm_notice(&engine->i915->drm, "%s heartbeat interval adjusted to a non-default value which may cause engine resets to target innocent contexts!\n",
+ engine->name);
+ }
+
intel_engine_pm_get(engine);
err = mutex_lock_interruptible(&ce->timeline->mutex);
--
2.37.3
