Date: Fri, 24 Mar 2017 13:07:42 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andi Kleen <ak@linux.intel.com>
cc: Kan Liang <kan.liang@intel.com>, peterz@infradead.org,
        mingo@redhat.com, acme@kernel.org, linux-kernel@vger.kernel.org,
        eranian@google.com, jolsa@kernel.org
Subject: Re: [PATCH 0/3]measure SMI cost
In-Reply-To: <20170324114051.GC9371@tassilo.jf.intel.com>
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On Fri, 24 Mar 2017, Andi Kleen wrote:

> > > A new --smi-cost mode in perf stat is implemented to measure the SMI cost
> > > by calculating cycles and aperf results. In practice, the percentages of
> > > SMI cycles should be more useful than absolute value.
> > 
> > That's only true for performance oriented analysis, but for analyzing the
> > root cause of latencies the actual cycles are definitely interesting.
> 
> perf stat also prints the absolute cycles of course (unless you do --metric-only)

So much for the theory. From the patch:

+                       if (!force_metric_only)
+                               metric_only = true;

> It cannot print individual cycles (per SMI occurrence), the only
> way to do that would be to poll constantly.

I'm well aware of that.

Thanks,

	tglx