Add entry for i915 new parallel submission uAPI plan.
v2: (Daniel Vetter): - Expand logical order explaination - Add dummy header - Only allow N BBs in execbuf IOCTL - Configure parallel submission per slot not per gem context v3: (Marcin Ślusarz): - Lot's of typos / bad english fixed (Tvrtko Ursulin): - Consistent pseudo code, clean up wording in descriptions
Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: Tony Ye tony.ye@intel.com CC: Carl Zhang carl.zhang@intel.com Cc: Daniel Vetter daniel.vetter@intel.com Cc: Jason Ekstrand jason@jlekstrand.net Signed-off-by: Matthew Brost matthew.brost@intel.com --- Documentation/gpu/rfc/i915_parallel_execbuf.h | 145 ++++++++++++++++++ Documentation/gpu/rfc/i915_scheduler.rst | 55 ++++++- 2 files changed, 198 insertions(+), 2 deletions(-) create mode 100644 Documentation/gpu/rfc/i915_parallel_execbuf.h
diff --git a/Documentation/gpu/rfc/i915_parallel_execbuf.h b/Documentation/gpu/rfc/i915_parallel_execbuf.h new file mode 100644 index 000000000000..20de206e3ab4 --- /dev/null +++ b/Documentation/gpu/rfc/i915_parallel_execbuf.h @@ -0,0 +1,145 @@ +#define I915_CONTEXT_ENGINES_EXT_PARALLEL_SUBMIT 2 /* see i915_context_engines_parallel_submit */ + +/* + * i915_context_engines_parallel_submit: + * + * Setup a slot in the context engine map to allow multiple BBs to be submitted + * in a single execbuf IOCTL. Those BBs will then be scheduled to run on the GPU + * in parallel. Multiple hardware contexts are created internally in the i915 + * run these BBs. Once a slot is configured for N BBs only N BBs can be + * submitted in each execbuf IOCTL and this is implicit behavior e.g. The user + * doesn't tell the execbuf IOCTL there are N BBs, the execbuf IOCTL know how + * many BBs there are based on the slots configuration. The N BBs are the last N + * buffer objects for first N if I915_EXEC_BATCH_FIRST is set. + * + * There are two currently defined ways to control the placement of the + * hardware contexts on physical engines: default behavior (no flags) and + * I915_PARALLEL_IMPLICIT_BONDS (a flag). More flags may be added the in the + * future as new hardware / use cases arise. Details of how to use this + * interface above the flags field in this structure. + * + * Returns -EINVAL if hardware context placement configuration is invalid or if + * the placement configuration isn't supported on the platform / submission + * interface. + * Returns -ENODEV if extension isn't supported on the platform / submission + * inteface. + */ +struct i915_context_engines_parallel_submit { + struct i915_user_extension base; + + __u16 engine_index; /* slot for parallel engine */ + __u16 width; /* number of contexts per parallel engine */ + __u16 num_siblings; /* number of siblings per context */ + __u16 mbz16; +/* + * Default placement behavior (currently unsupported): + * + * Allow BBs to be placed on any available engine instance. In this case each + * context's engine mask indicates where that context can be placed. It is + * implied in this mode that all contexts have mutual exclusive placement. + * e.g. If one context is running CSX[0] no other contexts can run on CSX[0]). + * + * Example 1 pseudo code: + * CSX,Y[N] = generic engine class X or Y, logical instance N + * INVALID = I915_ENGINE_CLASS_INVALID, I915_ENGINE_CLASS_INVALID_NONE + * set_engines(INVALID) + * set_parallel(engine_index=0, width=2, num_siblings=2, + * engines=CSX[0],CSX[1],CSY[0],CSY[1]) + * + * Results in the following valid placements: + * CSX[0], CSY[0] + * CSX[0], CSY[1] + * CSX[1], CSY[0] + * CSX[1], CSY[1] + * + * This can also be thought of as 2 virtual engines described by 2-D array in + * the engines the field: + * VE[0] = CSX[0], CSX[1] + * VE[1] = CSY[0], CSY[1] + * + * Example 2 pseudo code: + * CSX[Y] = generic engine of same class X, logical instance N + * INVALID = I915_ENGINE_CLASS_INVALID, I915_ENGINE_CLASS_INVALID_NONE + * set_engines(INVALID) + * set_parallel(engine_index=0, width=2, num_siblings=3, + * engines=CSX[0],CSX[1],CSX[2],CSX[0],CSX[1],CSX[2]) + * + * Results in the following valid placements: + * CSX[0], CSX[1] + * CSX[0], CSX[2] + * CSX[1], CSX[0] + * CSX[1], CSX[2] + * CSX[2], CSX[0] + * CSX[2], CSX[1] + * + * This can also be thought of as 2 virtual engines described by 2-D array in + * the engines the field: + * VE[0] = CSX[0], CSX[1], CSX[2] + * VE[1] = CSX[0], CSX[1], CSX[2] + + * This enables a use case where all engines are created equally, we don't care + * where they are scheduled, we just want a certain number of resources, for + * those resources to be scheduled in parallel, and possibly across multiple + * engine classes. + */ + +/* + * I915_PARALLEL_IMPLICIT_BONDS - Create implicit bonds between each context. + * Each context must have the same number of sibling and bonds are implicitly + * created between each set of siblings. + * + * Example 1 pseudo code: + * CSX[N] = generic engine of same class X, logical instance N + * INVALID = I915_ENGINE_CLASS_INVALID, I915_ENGINE_CLASS_INVALID_NONE + * set_engines(INVALID) + * set_parallel(engine_index=0, width=2, num_siblings=1, + * engines=CSX[0],CSX[1], flags=I915_PARALLEL_IMPLICIT_BONDS) + * + * Results in the following valid placements: + * CSX[0], CSX[1] + * + * Example 2 pseudo code: + * CSX[N] = generic engine of same class X, logical instance N + * INVALID = I915_ENGINE_CLASS_INVALID, I915_ENGINE_CLASS_INVALID_NONE + * set_engines(INVALID) + * set_parallel(engine_index=0, width=2, num_siblings=2, + * engines=CSX[0],CSX[2],CSX[1],CSX[3], + * flags=I915_PARALLEL_IMPLICIT_BONDS) + * + * Results in the following valid placements: + * CSX[0], CSX[1] + * CSX[2], CSX[3] + * + * This can also be thought of as 2 virtual engines described by 2-D array in + * the engines the field with bonds placed between each index of the virtual + * engines. e.g. CSX[0] is bonded to CSX[1], CSX[2] is bonded to CSX[3]. + * VE[0] = CSX[0], CSX[2] + * VE[1] = CSX[1], CSX[3] + * + * This enables a use case where all engines are not equal and certain placement + * rules are required (i.e. split-frame requires all contexts to be placed in a + * logically contiguous order on the VCS engines on gen11+ platforms). This use + * case (logically contiguous placement, within a single engine class) is + * supported when using GuC submission. Execlist mode could support all possible + * bonding configurations but currently doesn't support this extension. + */ +#define I915_PARALLEL_IMPLICIT_BONDS (1 << 0) +/* + * Do not allow BBs to be preempted mid BB rather insert coordinated preemption + * points on all hardware contexts between each set of BBs. An example use case + * of this feature is split-frame on gen11+ hardware. + */ +#define I915_PARALLEL_NO_PREEMPT_MID_BATCH (1 << 1) +#define __I915_PARALLEL_UNKNOWN_FLAGS (-(I915_PARALLEL_NO_PREEMPT_MID_BATCH << 1)) + __u64 flags; /* all undefined flags must be zero */ + __u64 mbz64[3]; /* reserved for future use; must be zero */ + + /* + * 2-D array of engines + * + * width (i) * num_siblings (j) in length + * index = j + i * num_siblings + */ + struct i915_engine_class_instance engines[0]; +} __attribute__ ((packed)); + diff --git a/Documentation/gpu/rfc/i915_scheduler.rst b/Documentation/gpu/rfc/i915_scheduler.rst index 7faa46cde088..0254c04d34be 100644 --- a/Documentation/gpu/rfc/i915_scheduler.rst +++ b/Documentation/gpu/rfc/i915_scheduler.rst @@ -23,7 +23,7 @@ i915 with the DRM scheduler is: 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 + 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 @@ -82,4 +82,55 @@ https://spec.oneapi.com/level-zero/latest/core/api.html#ze-command-queue-pri...
New parallel submission uAPI ============================ -Details to come in a following patch. +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. + +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 setup step that should 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 +support GuC submission. Execlist support can be added later if needed. + +Add I915_CONTEXT_ENGINES_EXT_PARALLEL_SUBMIT and +i915_context_engines_parallel_submit to the uAPI to implement this extension. + +Extend execbuf2 IOCTL to support submitting N BBs in a single IOCTL +------------------------------------------------------------------- +Contexts that have been configured with the 'set_parallel' extension are allowed +to 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 implict based on the slot +submitted and how it has been configured by 'set_parallel' or other extensions. +No uAPI changes are required to execbuf2 IOCTL.