From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> In i915 we have this concept of "wait boosting" where we give a priority boost for instance to fences which are actively waited upon from userspace. This has it's pros and cons and can certainly be discussed at lenght. However fact is some workloads really like it. Problem is that with the arrival of drm syncobj and a new userspace waiting entry point it added, the waitboost mechanism was bypassed. Hence I cooked up this mini series really (really) quickly to see if some discussion can be had. It adds a concept of "wait count" to dma fence, which is incremented for every explicit dma_fence_enable_sw_signaling and dma_fence_add_wait_callback (like dma_fence_add_callback but from explicit/userspace wait paths). Individual drivers can then inspect this via dma_fence_wait_count() and decide to wait boost the waits on such fences. Again, quickly put together and smoke tested only - no guarantees whatsoever and I will rely on interested parties to test and report if it even works or how well. Tvrtko Ursulin (3): dma-fence: Track explicit waiters drm/syncobj: Mark syncobj waits as external waiters drm/i915: Waitboost external waits drivers/dma-buf/dma-fence.c | 102 ++++++++++++++++++++-------- drivers/gpu/drm/drm_syncobj.c | 6 +- drivers/gpu/drm/i915/i915_request.c | 13 +++- include/linux/dma-fence.h | 14 ++++ 4 files changed, 101 insertions(+), 34 deletions(-) -- 2.34.1
