Acked-by: Michal Mrozek michal.mrozek@intel.com
-----Original Message----- From: Harrison, John C john.c.harrison@intel.com Sent: Thursday, March 3, 2022 11:38 PM To: Intel-GFX@Lists.FreeDesktop.Org Cc: DRI-Devel@Lists.FreeDesktop.Org; Harrison, John C john.c.harrison@intel.com; Ceraolo Spurio, Daniele daniele.ceraolospurio@intel.com; Mrozek, Michal michal.mrozek@intel.com Subject: [PATCH v3 4/4] drm/i915: Improve long running OCL w/a for GuC submission
From: John Harrison John.C.Harrison@Intel.com
A workaround was added to the driver to allow OpenCL 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 OpenCL 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 OpenCL 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 (v1) Acked-by: Michal Mrozek michal.mrozek@intel.com --- drivers/gpu/drm/i915/Kconfig.profile | 26 +++++++++++++++++++---- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 9 ++++++-- 2 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile index 39328567c200..7cc38d25ee5c 100644 --- a/drivers/gpu/drm/i915/Kconfig.profile +++ b/drivers/gpu/drm/i915/Kconfig.profile @@ -57,10 +57,28 @@ config DRM_I915_PREEMPT_TIMEOUT default 640 # milliseconds help How long to wait (in milliseconds) for a preemption event to occur - when submitting a new context via execlists. If the current context - does not hit an arbitration point and yield to HW before the timer - expires, the HW will be reset to allow the more important context - to execute. + when submitting a new context. If the current context does not hit + an arbitration point and yield to HW before the timer expires, the + HW will be reset to allow the more important context to execute. + + This is adjustable via + /sys/class/drm/card?/engine/*/preempt_timeout_ms + + May be 0 to disable the timeout. + + The compiled in default may get overridden at driver probe time on + certain platforms and certain engines which will be reflected in the + sysfs control. + +config DRM_I915_PREEMPT_TIMEOUT_COMPUTE + int "Preempt timeout for compute engines (ms, jiffy granularity)" + default 7500 # milliseconds + help + How long to wait (in milliseconds) for a preemption event to occur + when submitting a new context to a compute capable engine. If the + current context does not hit an arbitration point and yield to HW + before the timer expires, the HW will be reset to allow the more + important context to execute.
This is adjustable via /sys/class/drm/card?/engine/*/preempt_timeout_ms diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index 4185c7338581..cc0954ad836a 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -438,9 +438,14 @@ 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 OpenCL 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) \ -- 2.25.1