linux-kernel - Re: [PATCH v2] tracing: Don't account for cpu idle time with irqsoff tracers

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Message-ID: <20140528100910.6035ea7d@gandalf.local.home>
Date:	Wed, 28 May 2014 10:09:10 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Stephen Boyd <sboyd@...eaurora.org>, Arnd Bergmann <arnd@...db.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Corey Minyard <cminyard@...sta.com>,
	Stanislav Meduna <stano@...una.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, rjw@...ysocki.net
Subject: Re: [PATCH v2] tracing: Don't account for cpu idle time with
 irqsoff tracers

On Wed, 28 May 2014 09:28:52 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, May 27, 2014 at 07:30:50PM -0400, Steven Rostedt wrote:
> > Paul, Peter, see anything wrong with this?
> 
> You mean, aside from that it won't actually apply due to that code
> having been massively overhauled?
> 
> I suppose the same thing Arnd mentioned, the cpuidle_enter() thing can
> be huge, but is we're going to have to push this down into all cpuidle
> drivers we're not going to be happy.
> 

I believe that the stop/start_critical_timings() can nest. If not, I
can make them do so. Thus, we could start adding them in the depths of
the cpuidle drivers. If we miss one, we may not notice until someone
reports a large latency due to it.  And that is only if the driver
itself calls local_irq_save/restore().

-- Steve
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