Acked-by: Michal Mrozek <michal.mro...@intel.com>
-----Original Message-----
From: Harrison, John C <john.c.harri...@intel.com>
Sent: Thursday, March 3, 2022 11:38 PM
To: intel-...@lists.freedesktop.org
Cc: DRI-Devel@Lists.FreeDesktop.Org; Harrison, John C
<john.c.harri...@intel.com>; Ceraolo Spurio, Daniele
<daniele.ceraolospu...@intel.com>; Mrozek, Michal <michal.mro...@intel.com>
Subject: [PATCH v3 4/4] drm/i915: Improve long running OCL w/a for GuC
submission
From: John Harrison <john.c.harri...@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.harri...@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospu...@intel.com> (v1)
Acked-by: Michal Mrozek <michal.mro...@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
