linux-kernel - Re: [PATCH v2 1/2] trace: Default to using trace_global_clock if sched

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Message-ID: <20180402111736.763c861e@gandalf.local.home>
Date:   Mon, 2 Apr 2018 11:17:36 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v2 1/2] trace: Default to using trace_global_clock if
 sched_clock is unstable

On Fri, 30 Mar 2018 16:01:31 +0100
Chris Wilson <chris@...is-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@...is-wilson.co.uk>
> Cc: Steven Rostedt (VMware) <rostedt@...dmis.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.

-- Steve