linux-kernel - Re: [RFC/RFT] [PATCH 02/10] cpufreq: intel_pstate: Conditional frequency invariant accounting

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Message-ID: <20180516163105.GP28366@localhost.localdomain>
Date:   Wed, 16 May 2018 18:31:05 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...e.de, lenb@...nel.org,
        rjw@...ysocki.net, mgorman@...hsingularity.net, x86@...nel.org,
        linux-pm@...r.kernel.org, viresh.kumar@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC/RFT] [PATCH 02/10] cpufreq: intel_pstate: Conditional
 frequency invariant accounting

On 16/05/18 17:47, Peter Zijlstra wrote:
> On Wed, May 16, 2018 at 05:19:25PM +0200, Juri Lelli wrote:
> 
> > Anyway, FWIW I started testing this on a E5-2609 v3 and I'm not seeing
> > hackbench regressions so far (running with schedutil governor).
> 
> https://en.wikipedia.org/wiki/Haswell_(microarchitecture)#Server_processors
> 
> Lists the E5 2609 v3 as not having turbo at all, which is basically a
> best case scenario for this patch.
> 
> As I wrote earlier today; when turbo exists, like say the 2699, then
> when we're busy we'll run at U=2.3/3.6 ~ .64, which might confuse
> things.

Indeed. I was mostly trying to see if adding this to the tick might
introduce noticeable overhead.