mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-02 08:34:20 +08:00
0d7502fcd4
Update parallel submit doc to point to i915_drm.h Signed-off-by: Matthew Brost <matthew.brost@intel.com> Reviewed-by: John Harrison <John.C.Harrison@Intel.com> Signed-off-by: John Harrison <John.C.Harrison@Intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211014172005.27155-18-matthew.brost@intel.com
149 lines
7.0 KiB
ReStructuredText
149 lines
7.0 KiB
ReStructuredText
=========================================
|
|
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, no major coding style / layering errors, 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, plus it has
|
|
severe design issues in general, which is why we want to retire it no
|
|
matter what
|
|
* New uAPI adds I915_CONTEXT_ENGINES_EXT_PARALLEL context setup step
|
|
which configures a slot with N contexts
|
|
* After I915_CONTEXT_ENGINES_EXT_PARALLEL a user can submit N batches to
|
|
a slot 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...)
|
|
* Execlists backend will minimum required to hook in the DRM scheduler
|
|
* 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
|
|
* Used for i915 page flip, may be useful to other DRM drivers as
|
|
well
|
|
* Will be an optional feature in the DRM scheduler
|
|
* Remove in-order completion assumptions from DRM scheduler
|
|
* Even when using the DRM scheduler the backends will handle
|
|
preemption, timeslicing, etc... so it is possible for jobs to
|
|
finish out of order
|
|
* Pull out i915 priority levels and use DRM priority levels
|
|
* Optimize DRM scheduler as needed
|
|
|
|
TODOs for GuC submission upstream
|
|
=================================
|
|
|
|
* Need an update to GuC firmware / i915 to enable error state capture
|
|
* Open source tool to decode GuC logs
|
|
* Public GuC spec
|
|
|
|
New uAPI for basic GuC submission
|
|
=================================
|
|
No major changes are required to the uAPI for basic GuC submission. The only
|
|
change is a new scheduler attribute: I915_SCHEDULER_CAP_STATIC_PRIORITY_MAP.
|
|
This attribute indicates the 2k i915 user priority levels are statically mapped
|
|
into 3 levels as follows:
|
|
|
|
* -1k to -1 Low priority
|
|
* 0 Medium priority
|
|
* 1 to 1k High priority
|
|
|
|
This is needed because the GuC only has 4 priority bands. The highest priority
|
|
band is reserved with the kernel. This aligns with the DRM scheduler priority
|
|
levels too.
|
|
|
|
Spec references:
|
|
----------------
|
|
* https://www.khronos.org/registry/EGL/extensions/IMG/EGL_IMG_context_priority.txt
|
|
* https://www.khronos.org/registry/vulkan/specs/1.2-extensions/html/chap5.html#devsandqueues-priority
|
|
* https://spec.oneapi.com/level-zero/latest/core/api.html#ze-command-queue-priority-t
|
|
|
|
New parallel submission uAPI
|
|
============================
|
|
The existing bonding uAPI is completely broken with GuC submission because
|
|
whether a submission is a single context submit or parallel submit isn't known
|
|
until execbuf time activated via the I915_SUBMIT_FENCE. To submit multiple
|
|
contexts in parallel with the GuC the context must be explicitly registered with
|
|
N contexts and all N contexts must be submitted in a single command to the GuC.
|
|
The GuC interfaces do not support dynamically changing between N contexts as the
|
|
bonding uAPI does. Hence the need for a new parallel submission interface. Also
|
|
the legacy bonding uAPI is quite confusing and not intuitive at all. Furthermore
|
|
I915_SUBMIT_FENCE is by design a future fence, so not really something we should
|
|
continue to support.
|
|
|
|
The new parallel submission uAPI consists of 3 parts:
|
|
|
|
* Export engines logical mapping
|
|
* A 'set_parallel' extension to configure contexts for parallel
|
|
submission
|
|
* Extend execbuf2 IOCTL to support submitting N BBs in a single IOCTL
|
|
|
|
Export engines logical mapping
|
|
------------------------------
|
|
Certain use cases require BBs to be placed on engine instances in logical order
|
|
(e.g. split-frame on gen11+). The logical mapping of engine instances can change
|
|
based on fusing. Rather than making UMDs be aware of fusing, simply expose the
|
|
logical mapping with the existing query engine info IOCTL. Also the GuC
|
|
submission interface currently only supports submitting multiple contexts to
|
|
engines in logical order which is a new requirement compared to execlists.
|
|
Lastly, all current platforms have at most 2 engine instances and the logical
|
|
order is the same as uAPI order. This will change on platforms with more than 2
|
|
engine instances.
|
|
|
|
A single bit will be added to drm_i915_engine_info.flags indicating that the
|
|
logical instance has been returned and a new field,
|
|
drm_i915_engine_info.logical_instance, returns the logical instance.
|
|
|
|
A 'set_parallel' extension to configure contexts for parallel submission
|
|
------------------------------------------------------------------------
|
|
The 'set_parallel' extension configures a slot for parallel submission of N BBs.
|
|
It is a setup step that must be called before using any of the contexts. See
|
|
I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE or I915_CONTEXT_ENGINES_EXT_BOND for
|
|
similar existing examples. Once a slot is configured for parallel submission the
|
|
execbuf2 IOCTL can be called submitting N BBs in a single IOCTL. Initially only
|
|
supports GuC submission. Execlists supports can be added later if needed.
|
|
|
|
Add I915_CONTEXT_ENGINES_EXT_PARALLEL_SUBMIT and
|
|
drm_i915_context_engines_parallel_submit to the uAPI to implement this
|
|
extension.
|
|
|
|
.. kernel-doc:: include/uapi/drm/i915_drm.h
|
|
:functions: i915_context_engines_parallel_submit
|
|
|
|
Extend execbuf2 IOCTL to support submitting N BBs in a single IOCTL
|
|
-------------------------------------------------------------------
|
|
Contexts that have been configured with the 'set_parallel' extension can only
|
|
submit N BBs in a single execbuf2 IOCTL. The BBs are either the last N objects
|
|
in the drm_i915_gem_exec_object2 list or the first N if I915_EXEC_BATCH_FIRST is
|
|
set. The number of BBs is implicit based on the slot submitted and how it has
|
|
been configured by 'set_parallel' or other extensions. No uAPI changes are
|
|
required to the execbuf2 IOCTL.
|