linux-kernel - Re: [PATCH 2/4] perf stat: Add computation of TopDown formulas

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Date:	Wed, 1 Jun 2016 07:56:48 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Nilay Vaish <nilayvaish@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>, acme@...nel.org,
	jolsa@...nel.org, Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] perf stat: Add computation of TopDown formulas

On Wed, Jun 01, 2016 at 09:50:07AM -0500, Nilay Vaish wrote:
> On 24 May 2016 at 14:52, Andi Kleen <andi@...stfloor.org> wrote:
> > +static double td_be_bound(int ctx, int cpu)
> > +{
> > +       double sum = (td_fe_bound(ctx, cpu) +
> > +                     td_bad_spec(ctx, cpu) +
> > +                     td_retiring(ctx, cpu));
> > +       if (sum == 0)
> > +               return 0;
> > +       return sanitize_val(1.0 - sum);
> > +}
> > +
> 
> Can you explain why we need the check on sum?

You mean the if statement?

Otherwise if nothing was measured it would always report everything backend bound,
which wouldn't be correct.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only