linux-kernel - Re: [PATCH 0/3]measure SMI cost

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Message-ID: <20170324114051.GC9371@tassilo.jf.intel.com>
Date:   Fri, 24 Mar 2017 04:40:51 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Kan Liang <kan.liang@...el.com>, peterz@...radead.org,
        mingo@...hat.com, acme@...nel.org, linux-kernel@...r.kernel.org,
        eranian@...gle.com, jolsa@...nel.org
Subject: Re: [PATCH 0/3]measure SMI cost

> > 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)

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

-Andi