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From: "Javi Merino" <javi.merino@arm.com>
Date: Fri, 11 Jul 2014 09:27:55 +0100
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        Eduardo Valentin <edubezval@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@redhat.com>
Subject: Re: [RFC PATCH v5 09/10] thermal: add trace events to the power
 allocator governor
Message-ID: <20140711082755.GA2723@e104805>
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On Thu, Jul 10, 2014 at 07:03:50PM +0100, Steven Rostedt wrote:
> On Thu, 10 Jul 2014 17:20:14 +0100
> "Javi Merino" <javi.merino@arm.com> wrote:
> 
> 
> > > 
> > > How many CPUs are you saving load_cpu on? A trace event can't be bigger
> > > than a page. And the data is actually a little less than that with the
> > > required headers.
> > 
> > The biggest system I've tested it on is an 8 cpu system (with
> > NR_CPUS==8).  So yes, small and we haven't seen any issues.
> > 
> > Are you saying that we are siphoning too much data through ftrace?  He
> > find it really valuable to collect information during run and process
> > it afterwards but I can see how this may not be feasible for systems
> > with thousands of cpus.
> 
> Only too much for a single event. Perhaps have the tracepoint post per
> CPU? Then you wouldn't need that array.

Sounds good, I'll do that.