Quoting Koenig, Christian (2019-01-22 08:49:30) > Am 22.01.19 um 00:20 schrieb Chris Wilson: > > Rather than every backend and GPU driver reinventing the same wheel for > > user level debugging of HW execution, the common dma-fence framework > > should include the tracing infrastructure required for most client API > > level flow visualisation. > > > > With these common dma-fence level tracepoints, the userspace tools can > > establish a detailed view of the client <-> HW flow across different > > kernels. There is a strong ask to have this available, so that the > > userspace developer can effectively assess if they're doing a good job > > about feeding the beast of a GPU hardware. > > > > In the case of needing to look into more fine-grained details of how > > kernel internals work towards the goal of feeding the beast, the tools > > may optionally amend the dma-fence tracing information with the driver > > implementation specific. But for such cases, the tools should have a > > graceful degradation in case the expected extra tracepoints have > > changed or their format differs from the expected, as the kernel > > implementation internals are not expected to stay the same. > > > > It is important to distinguish between tracing for the purpose of client > > flow visualisation and tracing for the purpose of low-level kernel > > debugging. The latter is highly implementation specific, tied to > > a particular HW and driver, whereas the former addresses a common goal > > of user level tracing and likely a common set of userspace tools. > > Having made the distinction that these tracepoints will be consumed for > > client API tooling, we raise the spectre of tracepoint ABI stability. It > > is hoped that by defining a common set of dma-fence tracepoints, we avoid > > the pitfall of exposing low level details and so restrict ourselves only > > to the high level flow that is applicable to all drivers and hardware. > > Thus the reserved guarantee that this set of tracepoints will be stable > > (with the emphasis on depicting client <-> HW flow as opposed to > > driver <-> HW). > > > > In terms of specific changes to the dma-fence tracing, we remove the > > emission of the strings for every tracepoint (reserving them for > > dma_fence_init for cases where they have unique dma_fence_ops, and > > preferring to have descriptors for the whole fence context). strings do > > not pack as well into the ftrace ringbuffer and we would prefer to > > reduce the amount of indirect callbacks required for frequent tracepoint > > emission. > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > > Cc: Alex Deucher <alexdeucher@xxxxxxxxx> > > Cc: "Christian König" <christian.koenig@xxxxxxx> > > Cc: Eric Anholt <eric@xxxxxxxxxx> > > Cc: Pierre-Loup Griffais <pgriffais@xxxxxxxxxxxxxxxxx> > > Cc: Michael Sartain <mikesart@xxxxxxxxxxxx> > > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > > In general yes please! If possible please separate out the changes to > the common dma_fence infrastructure from the i915 changes. Sure, I was just stressing the impact: remove some randomly placed internal debugging tracepoints, try to define useful ones instead :) On the list of things to do was to convert at least 2 other drivers (I was thinking nouveau/msm for simplicity, vc4 for a simpler introduction to drm_sched than amdgpu) over to be sure we have the right tracepoints. > One thing I'm wondering is why the enable_signaling trace point doesn't > need to be exported any more. Is that only used internally in the common > infrastructure? Right. Only used inside the core, and I don't see much call for making it easy for drivers to fiddle around bypassing the core enable_signaling/signal. (I'm not sure it's useful for client flow either, it feels more like dma-fence debugging, but they can just not listen to that tracepoint.) -Chris _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
