On Thu, May 06, 2021 at 10:30:45AM -0700, Matthew Brost wrote:
> Add entry for i915 GuC submission / DRM scheduler integration plan.
> Follow up patch with details of new parallel submission uAPI to come.
>
> Cc: Jon Bloomfield
> Cc: Jason Ekstrand
> Cc: Dave Airlie
> Cc: Daniel Vetter
> Cc: Jason Ekstrand
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Matthew Brost
Would be good to Cc: some drm/scheduler folks here for the next round:
$ scripts/get_maintainer.pl -f -- drivers/gpu/drm/scheduler/
says we have maybe the following missing:
"Christian König"
Luben Tuikov
Alex Deucher
Steven Price
Lee Jones did a ton of warning fixes over the entire tree, so doesn't care
about drm/scheduler design directly.
> ---
> Documentation/gpu/rfc/i915_scheduler.rst | 70
> Documentation/gpu/rfc/index.rst | 4 ++
> 2 files changed, 74 insertions(+)
> create mode 100644 Documentation/gpu/rfc/i915_scheduler.rst
>
> diff --git a/Documentation/gpu/rfc/i915_scheduler.rst
> b/Documentation/gpu/rfc/i915_scheduler.rst
> new file mode 100644
> index ..fa6780a11c86
> --- /dev/null
> +++ b/Documentation/gpu/rfc/i915_scheduler.rst
> @@ -0,0 +1,70 @@
> +=
> +I915 GuC Submission/DRM Scheduler Section
> +=
> +
> +Upstream plan
> +=
> +For upstream the overall plan for landing GuC submission and integrating the
> +i915 with the DRM scheduler is:
> +
> +* Merge basic GuC submission
> + * Basic submission support for all gen11+ platforms
> + * Not enabled by default on any current platforms but can be enabled via
> + modparam enable_guc
> + * Lots of rework will need to be done to integrate with DRM scheduler so
> + no need to nit pick everything in the code, it just should be
> + functional and not regress execlists
> + * Update IGTs / selftests as needed to work with GuC submission
> + * Enable CI on supported platforms for a baseline
> + * Rework / get CI heathly for GuC submission in place as needed
> +* Merge new parallel submission uAPI
> + * Bonding uAPI completely incompatible with GuC submission
Maybe clarify that this isn't the only issue with the bonding uapi, so
perhaps add "Plus it has severe design issues in general, which is why we
want to retire it no matter what". Or something like that. Not sure we
should go into full details here, maybe as part of the next patch about
parallel submit and all that.
> + * New uAPI adds I915_CONTEXT_ENGINES_EXT_PARALLEL context setup step
> + which configures contexts N wide
> + * After I915_CONTEXT_ENGINES_EXT_PARALLEL a user can submit N batches to
> + a context in a single execbuf IOCTL and the batches run on the GPU in
> + paralllel
> + * Initially only for GuC submission but execlists can be supported if
> + needed
> +* Convert the i915 to use the DRM scheduler
> + * GuC submission backend fully integrated with DRM scheduler
> + * All request queues removed from backend (e.g. all backpressure
> + handled in DRM scheduler)
> + * Resets / cancels hook in DRM scheduler
> + * Watchdog hooks into DRM scheduler
> + * Lots of complexity of the GuC backend can be pulled out once
> + integrated with DRM scheduler (e.g. state machine gets
> + simplier, locking gets simplier, etc...)
> + * Execlist backend will do the minimum required to hook in the DRM
> + scheduler so it can live next to the fully integrated GuC backend
> + * Legacy interface
> + * Features like timeslicing / preemption / virtual engines would
> + be difficult to integrate with the DRM scheduler and these
> + features are not required for GuC submission as the GuC does
> + these things for us
> + * ROI low on fully integrating into DRM scheduler
> + * Fully integrating would add lots of complexity to DRM
> + scheduler
> + * Port i915 priority inheritance / boosting feature in DRM scheduler
Maybe a few words on what this does and why we care? Just so drm/scheduler
people know what's coming.
> + * Remove in-order completion assumptions from DRM scheduler
I think it'd be good to put a few words here why we need this. We want to
use drm scheduler for dependencies, but rely on the hw/fw scheduler (or
well backend for execlist) to handle preemption, round-robin and that kind
of stuff. Hence we want to have all runnable requests in the backend
(excluding backpressure and stuff like that), and they can complete
out-of-order.
Maybe also highlight this one in the commit message to get drm/scheduler
folks' attention on this and the previous one for discussion.
> + * Pull out i915 priority levels and use DRM priority levels
> + * Optimize DRM scheduler as needed
Agai
