linux-kernel - Re: [PATCH v2 2/2] cpufreq: CPPC: Dont read counters for idle CPUs

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Message-ID: <CAFivqmLSp6RwfsPBK0d=zvRd6M_5GoeU4jHb-0OM9BpaDeSrzA@mail.gmail.com>
Date: Wed, 6 Aug 2025 17:01:48 -0700
From: Prashant Malani <pmalani@...gle.com>
To: Beata Michalska <beata.michalska@....com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Jie Zhan <zhanjie9@...ilicon.com>, Ionela Voinescu <ionela.voinescu@....com>, 
	Ben Segall <bsegall@...gle.com>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, 
	open list <linux-kernel@...r.kernel.org>, 
	"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>, Mel Gorman <mgorman@...e.de>, 
	Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Valentin Schneider <vschneid@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	z00813676 <zhenglifeng1@...wei.com>, sudeep.holla@....com
Subject: Re: [PATCH v2 2/2] cpufreq: CPPC: Dont read counters for idle CPUs

Hi Beata,

On Wed, 6 Aug 2025 at 00:22, Beata Michalska <beata.michalska@....com> wrote:
> Would you mind giving it a go and see whether that improves things on your end ?
> Note that this is a quick and semi-dirty hack though.
>

Sure.
The provided patch doesn't appear to work as expected.
With all cores loaded (stress_ng --cpu N), it's returning the same
counter values
across samples. Here are readings from multiple CPUs:

t0: del:18446603338626579088, ref:192
t1: del:18446603338626579088, ref:192
ref_perf:10
delivered_perf:0


t0: del:18446603338627594896, ref:192
t1: del:18446603338627594896, ref:192
ref_perf:10
delivered_perf:0

t0: del:18446603338627627664, ref:192
t1: del:18446603338627627664, ref:192
ref_perf:10
delivered_perf:0

I verified separately that the "burst_read" path is being used by the platform
I am testing on.

BR,

-Prashant