a6149f0393
In Xe, the new Intel GPU driver, a choice has made to have a 1 to 1 mapping between a drm_gpu_scheduler and drm_sched_entity. At first this seems a bit odd but let us explain the reasoning below. 1. In Xe the submission order from multiple drm_sched_entity is not guaranteed to be the same completion even if targeting the same hardware engine. This is because in Xe we have a firmware scheduler, the GuC, which allowed to reorder, timeslice, and preempt submissions. If a using shared drm_gpu_scheduler across multiple drm_sched_entity, the TDR falls apart as the TDR expects submission order == completion order. Using a dedicated drm_gpu_scheduler per drm_sched_entity solve this problem. 2. In Xe submissions are done via programming a ring buffer (circular buffer), a drm_gpu_scheduler provides a limit on number of jobs, if the limit of number jobs is set to RING_SIZE / MAX_SIZE_PER_JOB we get flow control on the ring for free. A problem with this design is currently a drm_gpu_scheduler uses a kthread for submission / job cleanup. This doesn't scale if a large number of drm_gpu_scheduler are used. To work around the scaling issue, use a worker rather than kthread for submission / job cleanup. v2: - (Rob Clark) Fix msm build - Pass in run work queue v3: - (Boris) don't have loop in worker v4: - (Tvrtko) break out submit ready, stop, start helpers into own patch v5: - (Boris) default to ordered work queue v6: - (Luben / checkpatch) fix alignment in msm_ringbuffer.c - (Luben) s/drm_sched_submit_queue/drm_sched_wqueue_enqueue - (Luben) Update comment for drm_sched_wqueue_enqueue - (Luben) Positive check for submit_wq in drm_sched_init - (Luben) s/alloc_submit_wq/own_submit_wq v7: - (Luben) s/drm_sched_wqueue_enqueue/drm_sched_run_job_queue v8: - (Luben) Adjust var names / comments Signed-off-by: Matthew Brost <matthew.brost@intel.com> Reviewed-by: Luben Tuikov <luben.tuikov@amd.com> Link: https://lore.kernel.org/r/20231031032439.1558703-3-matthew.brost@intel.com Signed-off-by: Luben Tuikov <ltuikov89@gmail.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.