Re: [PATCH] arm64: add cpu_idle tracepoints to arch_cpu_idle

[Jisheng Zhang]

Dear Lorenzo,

On Wed, 16 Sep 2015 22:53:12 +0800
Jisheng Zhang <jszhang@xxxxxxxxxxx> wrote:

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

Maybe I know now. we need to trace different idle level, for example:

WFI idle: trace_cpu_idle_rcuidle(1, ...);

deeper idle: trace_cpu_idle_rcuidle(2, ...);

Usually, the first argument of trace_cpu_idle_rcuidle() equals to the index
of the idle level.

so generic idle loop is not a good candidate.

> 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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