linux-kernel - Re: [PATCH v6 2/2] tracing: Add support for preempt and irq enable/disable events

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Date:   Mon, 25 Sep 2017 06:52:26 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Joel Fernandes <joelaf@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@...roid.com
Subject: Re: [PATCH v6 2/2] tracing: Add support for preempt and irq
 enable/disable events

On Mon, 25 Sep 2017 12:32:23 +0200
Peter Zijlstra <peterz@...radead.org> wrote:


> > You mean you want to trace all calls to preempt and irq off even if
> > preempt and irqs are already off?  
> 
> Sure, why not? This stuff naturally nests, and who is to say its not a
> useful thing to trace all of them?
> 
> By also tracing the nested sections you can, for instance, see how much
> you'd really win by getting rid of the outer one. If, for instance, the
> outer only accounts for 1% of the time, while the inner ones are
> interlinked and span the other 99%, there's more work to do than if that
> were not the case.

If we do this we need a field to record if the preemption or irqs were
toggled by that call. Something that filters could easily be added to
only show what this patch set has.

-- Steve