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drm/i915: Improve long running compute w/a for GuC submission

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A workaround was added to the driver to allow compute workloads to run
'forever' by disabling pre-emption on the RCS engine for Gen12.
It is not totally unbound as the heartbeat will kick in eventually
and cause a reset of the hung engine.

However, this does not work well in GuC submission mode. In GuC mode,
the pre-emption timeout is how GuC detects hung contexts and triggers
a per engine reset. Thus, disabling the timeout means also losing all
per engine reset ability. A full GT reset will still occur when the
heartbeat finally expires, but that is a much more destructive and
undesirable mechanism.

The purpose of the workaround is actually to give compute tasks longer
to reach a pre-emption point after a pre-emption request has been
issued. This is necessary because Gen12 does not support mid-thread
pre-emption and compute tasks can have long running threads.

So, rather than disabling the timeout completely, just set it to a
'long' value.

v2: Review feedback from Tvrtko - must hard code the 'long' value
instead of determining it algorithmically. So make it an extra CONFIG
definition. Also, remove the execlist centric comment from the
existing pre-emption timeout CONFIG option given that it applies to
more than just execlists.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Acked-by: Michal Mrozek <michal.mrozek@intel.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221006213813.1563435-5-John.C.Harrison@Intel.com
This commit is contained in:
John Harrison
2022-10-06 14:38:13 -07:00
parent 47daf84a8b
commit d7a8680ec9
2 changed files with 29 additions and 6 deletions
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9
drivers/gpu/drm/i915/gt/intel_engine_cs.c
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@@ -508,9 +508,14 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
engine->props.timeslice_duration_ms =
CONFIG_DRM_I915_TIMESLICE_DURATION;
/* Override to uninterruptible for OpenCL workloads. */
/*
* Mid-thread pre-emption is not available in Gen12. Unfortunately,
* some compute workloads run quite long threads. That means they get
* reset due to not pre-empting in a timely manner. So, bump the
* pre-emption timeout value to be much higher for compute engines.
*/
if (GRAPHICS_VER(i915) == 12 && (engine->flags & I915_ENGINE_HAS_RCS_REG_STATE))
engine->props.preempt_timeout_ms = 0;
engine->props.preempt_timeout_ms = CONFIG_DRM_I915_PREEMPT_TIMEOUT_COMPUTE;
/* Cap properties according to any system limits */
#define CLAMP_PROP(field) \