linux-kernel - Re: [PATCH 6/7] thermal: netlink: Add a new event to notify CPU capabilities change

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Message-ID: <2160a0b8-59ec-03a1-1fd5-a3f98085be07@arm.com>
Date:   Tue, 9 Nov 2021 12:39:40 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-pm@...r.kernel.org, x86@...nel.org,
        linux-doc@...r.kernel.org, Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Amit Kucheria <amitk@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] thermal: netlink: Add a new event to notify CPU
 capabilities change

Hi Ricardo,


On 11/6/21 1:33 AM, Ricardo Neri wrote:
> From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> 
> Add a new netlink event to notify change in CPU capabilities in terms of
> performance and efficiency.

Is this going to be handled by some 'generic' tools? If yes, maybe
the values for 'performance' might be aligned with capacity
[0,1024] ? Or are they completely not related so the mapping is
simply impossible?

> 
> Firmware may change CPU capabilities as a result of thermal events in the
> system or to account for changes in the TDP (thermal design power) level.
> 
> This notification type will allow user space to avoid running workloads
> on certain CPUs or proactively adjust power limits to avoid future events.
> 
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Aubrey Li <aubrey.li@...ux.intel.com>
> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> Cc: "Ravi V. Shankar" <ravi.v.shankar@...el.com>
> Reviewed-by: Len Brown <len.brown@...el.com>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
>   drivers/thermal/thermal_netlink.c | 52 +++++++++++++++++++++++++++++++
>   drivers/thermal/thermal_netlink.h | 13 ++++++++
>   include/uapi/linux/thermal.h      |  6 +++-
>   3 files changed, 70 insertions(+), 1 deletion(-)

[snip]

>   
> +struct cpu_capability {
> +	int cpu;
> +	int perf;
> +	int eff;

Why not use the full names, instead of thse shortcuts? We use full
naming e.g. in cpufreq framework such as 'frequency' not 'freq'.
The 'eff' is really not meaningful ('perf' a bit less but it has
to meanings in kernel).

Regards,
Lukasz