Commit 47daf84a authored by John Harrison's avatar John Harrison
Browse files

drm/i915: Make the heartbeat play nice with long pre-emption timeouts 



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: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221006213813.1563435-4-John.C.Harrison@Intel.com
parent c3bd49cd

drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c

+39 −0
Original line number Diff line number Diff line
@@ -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);