On Thu, 7 Nov 2019 16:02:59 -0500 Sean Paul <sean@xxxxxxxxxx> wrote: > From: Sean Paul <seanpaul@xxxxxxxxxxxx> > > Hey all, > I'm back with another trace events patchset. My first attempt [1] went > better than expected, with enthusiasm for the idea and distain for the > implementation. > > As promised, I went through and added proper trace events. > > Before I get _too_ far, I wanted to post this set to get feedback on the > direction I'm going. I've gone back and forth on whether to introduce a > bunch of trace systems vs using the trace class enum. I've settled on > the trace class enum since it seems more extensible and easier to use in > production that just having the blunt "enable this system", or > the tedious "enable each event I'm interested in individually" methods. > > So, consider this one an RFC unless we're all in agreement, in which > case we should apply it :) > Hi Sean, thanks for working on this. I'm not at all familiar with the trace infrastructure, so I'd like to know how flight recorder type of behaviour (a continuously written fixed size ring buffer) can be achieved. Let us have a display server in userspace which in production hits an unexpected condition with DRM and needs to record information for post-mortem debugging. What should it do to have a trace log after the fact to attach with a bug report? I assume that is a major use case for this new feature. Is performance profiling another use case? Is it ok to build userspace to rely on these trace events during normal operations, e.g. for continuous adjustment of timings/timers? Thanks, pq > > [1]- https://patchwork.freedesktop.org/patch/335350/ > > Sean Paul (6): > drm: trace: Make the vblank queued/delivered events classed > drm: trace: Introduce drm_trace() and trace event classes > drm: trace: Add trace events for atomic state lifetime > drm: trace: Add crtc state trace events > drm: trace: Add connector state tracing > drm: trace: Add plane state tracing > > Documentation/gpu/drm-internals.rst | 9 + > drivers/gpu/drm/drm_atomic.c | 61 ++- > drivers/gpu/drm/drm_trace.h | 563 ++++++++++++++++++++++++++-- > drivers/gpu/drm/drm_vblank.c | 8 +- > 4 files changed, 609 insertions(+), 32 deletions(-) >
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