linux-kernel - Re: [PATCH] trace power_frequency events on the correct cpu (for Intel x86 CPUs)

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Date:	Tue, 30 Mar 2010 07:46:55 +0200
From:	Robert Schöne <robert.schoene@...dresden.de>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Thomas Renninger <trenn@...e.de>, Dave Jones <davej@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	cpufreq <cpufreq@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH] trace power_frequency events on the correct cpu  (for
 Intel x86 CPUs)

Am Mittwoch, den 24.03.2010, 08:07 +0100 schrieb Robert Schöne:
> Am Dienstag, den 23.03.2010, 09:58 -0700 schrieb Arjan van de Ven:
> > On 3/23/2010 9:57, Thomas Renninger wrote:
> > > On Tuesday 23 March 2010 17:28:36 Robert SchÃ¶ne wrote:
> > >> Am Montag, den 22.03.2010, 06:57 -0700 schrieb Arjan van de Ven:
> > >>> On 3/22/2010 0:04, Robert SchÃ¶ne wrote:
> > >>>> Am Sonntag, den 21.03.2010, 17:42 -0700 schrieb Arjan van de Ven:
> > >>>>> On 3/20/2010 14:37, Thomas Renninger wrote:
> > >>>>>
> > >>>>>> It also seem to be (hopefully) a minor feature for timechart, so this should
> > >>>>>> not hurt that much (yet).
> > >>>>>
> > >>>>> It's actually a major feature for timechart, and one of the key things I and a bunch of others
> > >>>>> inside Intel use timechart for.
> > >>>>>
> > >>>> It's a major feature for us too.
> > >>>> I suppose, the cpufreq_notify_transition calls are correct (meaning
> > >>>> being called for all related cpus) for every driver. So there's still
> > >>>> the option to include it in the POST_CHANGE section of this function.
> > >>>> Could this be okay for the both of you?
> > >>>
> > >>> post change would work... that gets frequency afaik..
> > >> Are you ok with this too, Thomas?
> > > You mean hooking it into cpufreq_stat_notifier_trans() in
> > > drivers/cpufreq/cpufreq_stats.c?
> > 
> > no
> > 
> > 
> > hooking into the post frequency change callback that gets done..
> > which is guaranteed to be on the right cpu afaics.
> > 
> I don't see where this would be guaranteed. So I'd be fine with
> a) adding it to
> cpufreq.c/cpufreq_notify_transition/cpufreq_notify_transition
> 
> b) adding an item to the cpufreq_transition_notifier_list
> 
> c) adding it to cpufreq_stats.c/cpufreq_stat_notifier_trans
> 
> which would imply the usage of smp_call_function_single(...)
> 
I really want to keep this diskussion alive until there's a soultion we
can all agree.
So Arjan and Thomas, are there any comments/preferences to the proposed
options?


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