linux-kernel - Re: sched_clock and device suspend/resume

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Message-ID: <alpine.DEB.2.21.1907102034190.1758@nanos.tec.linutronix.de>
Date:   Wed, 10 Jul 2019 20:35:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
cc:     Sodagudi Prasad <psodagud@...eaurora.org>,
        pasha.tatashin@...cle.com, gregkh@...uxfoundation.org,
        sboyd@...eaurora.org, john.stultz@...aro.org,
        chang-an.chen@...iatek.com, mingo@...nel.org, pmladek@...e.com,
        sergey.senozhatsky@...il.com, linux-kernel@...r.kernel.org,
        tsoni@...eaurora.org
Subject: Re: sched_clock and device suspend/resume

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@...eaurora.org> 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