On Tue, Jan 22, 2019 at 10:06 AM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > 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. I think sprinkling these over the scheduler (maybe just as an opt-in, for the case where the driver doesn't have some additional queueing somewhere) would be good. I haven't checked whether it fits, but would give you a bunch of drivers at once. It might also not cover all the cases (I guess the wait related ones would need to be somewhere else). -Daniel > > 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 -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
