[Intel-gfx] [PATCH v2 1/2] trace: Default to using trace_global_clock if sched_clock is unstable

[Chris Wilson]

Quoting Steven Rostedt (2018-04-02 16:17:36)
> On Fri, 30 Mar 2018 16:01:31 +0100
> Chris Wilson <chris at chris-wilson.co.uk> wrote:
> 
> > Across suspend, we may see a very large drift in timestamps if the sched
> > clock is unstable, prompting the global trace's ringbuffer code to warn
> > and suggest switching to the global clock. Preempt this request by
> > detecting when the sched clock is unstable (determined during
> > late_initcall) and automatically switching the default clock over to
> > trace_global_clock.
> > 
> > This should prevent requiring user interaction to resolve warnings such
> > as:
> > 
> >     Delta way too big! 18446743856563626466 ts=18446744054496180323 write stamp = 197932553857
> >     If you just came from a suspend/resume,
> >     please switch to the trace global clock:
> >     echo global > /sys/kernel/debug/tracing/trace_clock
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Steven Rostedt (VMware) <rostedt at goodmis.org>
> > ---
> > v2: Tell the user what's happening and what they can do to correct it.
> >
> 
> Thanks, I pulled them in. I'll start testing them before I post to git.

Ta, I've pushed them onto our local CI branch to be superseded when they
land upstream. If you see any problems, just holler.
-Chris