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SubjectRe: [PATCHv2] trace: adding unstable sched clock note to the warning
hi,
any feedback?

thanks,
jirka

On Fri, Feb 18, 2011 at 03:52:19PM +0100, Jiri Olsa wrote:
> hi,
>
> warning "Delta way too big" warning might appear on a system with
> unstable shed clock right after the system is resumed and tracing
> was enabled during the suspend.
>
> Since it's not realy bug, and the unstable sched clock is working
> fast and reliable otherwise, Steven suggested to keep using the
> sched clock in any case and just to make note in the warning itself.
>
> v2 changes:
> - added CONFIG_HAVE_UNSTABLE_SCHED_CLOCK dependency
>
> wbr,
> jirka
>
>
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>
> ---
> kernel/trace/ring_buffer.c | 12 ++++++++++--
> 1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index bd1c35a..37c4d3e 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -2162,11 +2162,19 @@ rb_reserve_next_event(struct ring_buffer *buffer,
> if (likely(ts >= cpu_buffer->write_stamp)) {
> delta = diff;
> if (unlikely(test_time_stamp(delta))) {
> + int local_clock_stable = 1;
> +#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
> + local_clock_stable = sched_clock_stable;
> +#endif
> WARN_ONCE(delta > (1ULL << 59),
> - KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n",
> + KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
> (unsigned long long)delta,
> (unsigned long long)ts,
> - (unsigned long long)cpu_buffer->write_stamp);
> + (unsigned long long)cpu_buffer->write_stamp,
> + local_clock_stable ? "" :
> + "If you just came from a suspend/resume,\n"
> + "please switch to the trace global clock:\n"
> + " echo global > /sys/kernel/debug/tracing/trace_clock\n");
> add_timestamp = 1;
> }
> }
> --
> 1.7.1
> --
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