[Intel-gfx] [PATCH 2/3] drm/i915/gt: Make the heartbeat play nice with long pre-emption timeouts

John.C.Harrison
2022-02-18T21:33:18Z

From: John Harrison <John.C.Harrison@Intel.com>

Compute workloads are inherantly 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
magnititude.

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.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
---
drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index a3698f611f45..72a82a6085e0 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -22,9 +22,25 @@

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;
+ if (rq && rq->sched.attr.priority >= I915_PRIORITY_BARRIER) {
+ 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;
+ if (longer > delay)
+ delay = longer;
+ }
+
if (!delay)
return false;

--
2.25.1