linux-kernel - Re: Patch for tracing c states (power

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Message-ID: <4B84E51A.900@cn.fujitsu.com>
Date:	Wed, 24 Feb 2010 16:36:42 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Robert Schöne <robert.schoene@...dresden.de>
CC:	Arjan van de Ven <arjan@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: Patch for tracing c states (power_end) on x86

Robert Schöne wrote:
> Hello,
> 
> Since noone replied to my last mail (Febr. 15th, 11:42), describing the
> way to fix the missing c-state tracing, here's a patch.
> Maybe its easier that way.
> 
> (I used the perf-fixes-for-linus git tree to obtain a
> more-then-up-to-date version)
> 
> Bye Robert
> 
> 
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 02d6780..b1cfb88 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -384,6 +384,7 @@ void default_idle(void)
>                 else
>                         local_irq_enable();
>                 current_thread_info()->status |= TS_POLLING;
> +               trace_power_end(1);
>         } else {
>                 local_irq_enable();
>                 /* loop is done by the caller */
> @@ -451,6 +452,7 @@ void mwait_idle_with_hints(unsigned long ax,
> unsigned long cx)
>                 if (!need_resched())
>                         __mwait(ax, cx);
>         }
> +       trace_power_end((ax>>4)+1);

The only argument of trace_power_end() is a dummy, so you can just
pass 0 or 1 to the trace hook, actually better pass 0 to be
consistent with other parts.

The dummy argument can't be eliminated, because the macros that
automatically generates racing code have some limitations, and
seems it's not so easy to get over.

>  }
>  
>  /* Default MONITOR/MWAIT with no hints, used for default C1 state */
> @@ -467,6 +469,7 @@ static void mwait_idle(void)
>                         __sti_mwait(0, 0);
>                 else
>                         local_irq_enable();
> +               trace_power_end(1);
>         } else
>                 local_irq_enable();
>  }
> 
> 
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