From: "Liang, Kan" <kan.liang@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>, Andi Kleen <ak@linux.intel.com>
CC: "peterz@infradead.org" <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "acme@kernel.org" <acme@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "eranian@google.com" <eranian@google.com>,
        "jolsa@kernel.org" <jolsa@kernel.org>
Subject: RE: [PATCH 0/3]measure SMI cost
Thread-Topic: [PATCH 0/3]measure SMI cost
Thread-Index: AQHSpARyK/EZaqE9Zk+BnaMVBcLFrKGjJ56AgAAxNoCAAAeBAIAApDSA
Date: Fri, 24 Mar 2017 14:14:03 +0000
Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077536C3CBC@SHSMSX103.ccr.corp.intel.com>
References: <1490293551-5552-1-git-send-email-kan.liang@intel.com>
 <alpine.DEB.2.20.1703240942590.3688@nanos>
 <20170324114051.GC9371@tassilo.jf.intel.com>
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> 
> > > > 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;
> 

The metric_only will be set by default in the patch. If user wants to get
the actual cycles, they can apply --no-metric-only. 

Do you want me to make it clear in the changelog? Or you just don't like
that "metric_only=true" is set by default?


Thanks,
Kan