Re: sched_clock and device suspend/resume

From: Thomas Gleixner
Date: Wed Jul 10 2019 - 14:36:00 EST


On Wed, 10 Jul 2019, Steven Rostedt wrote:

>
> [ Resending as your Cc was screwed up and caused my reply to mess up
> the Cc list ]
>
> On Wed, 10 Jul 2019 08:20:37 -0700
> Sodagudi Prasad <psodagud@xxxxxxxxxxxxxx> wrote:
>
> > Another option is printing the epoch/cycles information in every print
> > statement similar to thread id or processor id added
> > recently(CONFIG_PRINTK_CALLER). This can be avoided if we start
> > accounting suspend time in sched_clock.
>
> Or another option is add a new clock that printk and tracing can use.
> tracing already can switch between clocks trivially.
>
> sched_clock_continuous() ? (I know, horrible name), that simply keeps
> track of the time delta at suspend and returns:
>
> sched_clock() + delta;

Which you get already when you do

# echo boot > /sys/kernel/debug/tracing/trace_clock

Thanks,

tglx