i915_scheduler.rst - OpenGrok cross reference for /linux/Documentation/gpu/rfc/i915

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i915_scheduler.rst (f587623b78ff538f5d9ef1241e58b91ea70a4daf)	i915_scheduler.rst (0454a490bdebea78e93e325a020f9f80908b9ed6)
1========================================= 2I915 GuC Submission/DRM Scheduler Section 3========================================= 4 5Upstream plan 6============= 7For upstream the overall plan for landing GuC submission and integrating the 8i915 with the DRM scheduler is: --- 74 unchanged lines hidden (view full) --- 83Spec references: 84---------------- 85* https://www.khronos.org/registry/EGL/extensions/IMG/EGL_IMG_context_priority.txt 86* https://www.khronos.org/registry/vulkan/specs/1.2-extensions/html/chap5.html#devsandqueues-priority 87* https://spec.oneapi.com/level-zero/latest/core/api.html#ze-command-queue-priority-t 88 89New parallel submission uAPI 90============================	1========================================= 2I915 GuC Submission/DRM Scheduler Section 3========================================= 4 5Upstream plan 6============= 7For upstream the overall plan for landing GuC submission and integrating the 8i915 with the DRM scheduler is: --- 74 unchanged lines hidden (view full) --- 83Spec references: 84---------------- 85* https://www.khronos.org/registry/EGL/extensions/IMG/EGL_IMG_context_priority.txt 86* https://www.khronos.org/registry/vulkan/specs/1.2-extensions/html/chap5.html#devsandqueues-priority 87* https://spec.oneapi.com/level-zero/latest/core/api.html#ze-command-queue-priority-t 88 89New parallel submission uAPI 90============================
91Details to come in a following patch.	91The existing bonding uAPI is completely broken with GuC submission because 92whether a submission is a single context submit or parallel submit isn't known 93until execbuf time activated via the I915_SUBMIT_FENCE. To submit multiple 94contexts in parallel with the GuC the context must be explicitly registered with 95N contexts and all N contexts must be submitted in a single command to the GuC. 96The GuC interfaces do not support dynamically changing between N contexts as the 97bonding uAPI does. Hence the need for a new parallel submission interface. Also 98the legacy bonding uAPI is quite confusing and not intuitive at all. Furthermore 99I915_SUBMIT_FENCE is by design a future fence, so not really something we should 100continue to support. 101 102The new parallel submission uAPI consists of 3 parts: 103 104* Export engines logical mapping 105* A 'set_parallel' extension to configure contexts for parallel 106 submission 107* Extend execbuf2 IOCTL to support submitting N BBs in a single IOCTL 108 109Export engines logical mapping 110------------------------------ 111Certain use cases require BBs to be placed on engine instances in logical order 112(e.g. split-frame on gen11+). The logical mapping of engine instances can change 113based on fusing. Rather than making UMDs be aware of fusing, simply expose the 114logical mapping with the existing query engine info IOCTL. Also the GuC 115submission interface currently only supports submitting multiple contexts to 116engines in logical order which is a new requirement compared to execlists. 117Lastly, all current platforms have at most 2 engine instances and the logical 118order is the same as uAPI order. This will change on platforms with more than 2 119engine instances. 120 121A single bit will be added to drm_i915_engine_info.flags indicating that the 122logical instance has been returned and a new field, 123drm_i915_engine_info.logical_instance, returns the logical instance. 124 125A 'set_parallel' extension to configure contexts for parallel submission 126------------------------------------------------------------------------ 127The 'set_parallel' extension configures a slot for parallel submission of N BBs. 128It is a setup step that must be called before using any of the contexts. See 129I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE or I915_CONTEXT_ENGINES_EXT_BOND for 130similar existing examples. Once a slot is configured for parallel submission the 131execbuf2 IOCTL can be called submitting N BBs in a single IOCTL. Initially only 132supports GuC submission. Execlists supports can be added later if needed. 133 134Add I915_CONTEXT_ENGINES_EXT_PARALLEL_SUBMIT and 135drm_i915_context_engines_parallel_submit to the uAPI to implement this 136extension. 137 138.. kernel-doc:: Documentation/gpu/rfc/i915_parallel_execbuf.h 139 :functions: drm_i915_context_engines_parallel_submit 140 141Extend execbuf2 IOCTL to support submitting N BBs in a single IOCTL 142------------------------------------------------------------------- 143Contexts that have been configured with the 'set_parallel' extension can only 144submit N BBs in a single execbuf2 IOCTL. The BBs are either the last N objects 145in the drm_i915_gem_exec_object2 list or the first N if I915_EXEC_BATCH_FIRST is 146set. The number of BBs is implicit based on the slot submitted and how it has 147been configured by 'set_parallel' or other extensions. No uAPI changes are 148required to the execbuf2 IOCTL.