Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency
 invariance
To:     Viresh Kumar <viresh.kumar@linaro.org>
CC:     Rafael Wysocki <rjw@rjwysocki.net>,
        Ionela Voinescu <ionela.voinescu@arm.com>,
        Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Mel Gorman <mgorman@suse.de>,
        Peter Zijlstra <peterz@infradead.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Will Deacon <will@kernel.org>, <linux-pm@vger.kernel.org>,
        <linux-acpi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
References: <cover.1624266901.git.viresh.kumar@linaro.org>
 <09a39f5c-b47b-a931-bf23-dc43229fb2dd@quicinc.com>
 <20210623041613.v2lo3nidpgw37abl@vireshk-i7>
From:   Qian Cai <quic_qiancai@quicinc.com>
Message-ID: <2c540a58-4fef-5a3d-85b4-8862721b6c4f@quicinc.com>
Date:   Wed, 23 Jun 2021 08:57:46 -0400
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <20210623041613.v2lo3nidpgw37abl@vireshk-i7>
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 6/23/2021 12:16 AM, Viresh Kumar wrote:
> On 21-06-21, 16:48, Qian Cai wrote:
>>
>>
>> On 6/21/2021 5:19 AM, Viresh Kumar wrote:
>>> CPPC cpufreq driver is used for ARM servers and this patch series tries to
>>> provide counter-based frequency invariance support for them in the absence for
>>> architecture specific counters (like AMUs).
>>
>> Viresh, this series works fine on my quick tests so far.
> 
> Do you want me to add your Tested-by for the series ?

Viresh, I am afraid I don't feel comfortable yet. I have a few new tests in development, and will provide an update once ready. Also, I noticed the delivered perf is even smaller than lowest_perf (100).

# cat /sys/devices/system/cpu/cpu8/acpi_cppc/feedback_ctrs
 ref:103377547901 del:54540736873
# cat /sys/devices/system/cpu/cpu8/acpi_cppc/feedback_ctrs
 ref:103379170101 del:54541599117

100 * (54541599117 - 54540736873) / (103379170101 - 103377547901) = 53

My understanding is that the delivered perf should fail into the range between lowest_perf and highest_perf. Is that assumption correct? This happens on 5.4-based kernel, so I am in process running your series on that system to see if there is any differences. In any case, if it is a bug it is pre-existing, but I'd like to understand a bit better in that front first.