linux-kernel - Re: [PATCH] arm64: add cpu_idle tracepoints to arch_cpu

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Date:	Wed, 16 Sep 2015 22:53:12 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: add cpu_idle tracepoints to arch_cpu_idle

Dear Lorenzo,

On Wed, 16 Sep 2015 15:47:38 +0100
Lorenzo Pieralisi <lorenzo.pieralisi@....com> wrote:

> On Wed, Sep 16, 2015 at 03:23:21PM +0100, Jisheng Zhang wrote:
> > Currently, if cpuidle is disabled or not supported, powertop reports
> > zero wakeups and zero events. This is due to the cpu_idle tracepoints
> > are missing.
> > 
> > This patch is to make cpu_idle tracepoints always available even if
> > cpuidle is disabled or not supported.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> 
> Is there a reason why this code cannot be moved to the generic idle loop ?

Do you mean the cpu_idle_loop() in kernel/sched/idle.c? To be honest, I
dunno. Maybe kernel experts can give some hints.

Thanks,
Jisheng

> 
> Thanks,
> Lorenzo
> 
> > ---
> >  arch/arm64/kernel/process.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> > index 223b093..f75b540 100644
> > --- a/arch/arm64/kernel/process.c
> > +++ b/arch/arm64/kernel/process.c
> > @@ -44,6 +44,7 @@
> >  #include <linux/hw_breakpoint.h>
> >  #include <linux/personality.h>
> >  #include <linux/notifier.h>
> > +#include <trace/events/power.h>
> >  
> >  #include <asm/compat.h>
> >  #include <asm/cacheflush.h>
> > @@ -75,8 +76,10 @@ void arch_cpu_idle(void)
> >  	 * This should do all the clock switching and wait for interrupt
> >  	 * tricks
> >  	 */
> > +	trace_cpu_idle_rcuidle(1, smp_processor_id());
> >  	cpu_do_idle();
> >  	local_irq_enable();
> > +	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
> >  }
> >  
> >  #ifdef CONFIG_HOTPLUG_CPU
> > -- 
> > 2.5.1
> > 
> > --
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> > 

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