linux-kernel - Re: [PATCH v2] cpuidle: psci: Add trace for PSCI domain idle

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Message-ID: <f697970e-3796-41cb-9904-d61cbedec428@arm.com>
Date: Tue, 28 Jan 2025 11:06:00 +0000
From: Christian Loehle <christian.loehle@....com>
To: Keita Morisaki <keyz@...gle.com>
Cc: aarontian@...gle.com, daniel.lezcano@...aro.org,
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, lpieralisi@...nel.org,
 mathieu.desnoyers@...icios.com, mhiramat@...nel.org, rafael@...nel.org,
 rostedt@...dmis.org, sudeep.holla@....com, yimingtseng@...gle.com
Subject: Re: [PATCH v2] cpuidle: psci: Add trace for PSCI domain idle

On 1/28/25 04:24, Keita Morisaki wrote:
>>> The trace event cpu_idle provides insufficient information for debugging
>>> PSCI requests due to lacking access to determined PSCI domain idle
>>> states. The cpu_idle usually only shows -1, 0, or 1 regardless how many
>>> idle states the power domain has.
>>>
>>> Add new trace events namely psci_domain_idle_enter and
>>> psci_domain_idle_exit to trace enter and exit events with a determined
>>> idle state.
>>>
>>> These new trace events will help developers debug CPUidle issues on ARM
>>> systems using PSCI by providing more detailed information about the
>>> requested idle states.
>>>
>>> Signed-off-by: Keita Morisaki <keyz@...gle.com>
>>> ---
>>> v1->v2: Split the ftrace event into two (psci_domain_idle_(enter|exit))
>>> 		and rephrase the commit message accordingly. Rebased onto the latest.
>> Which makes it different to cpu_idle event FWIW.
> 
> Yes, psci_domain_idle_(enter|exit) are not meant to replace cpu_idle nor a
> variant of it. It's new and different events that provide finer=grained info.
> 

I mentioned it because it means it doesn't benefit from cpu_idle tooling
directly, which is slightly odd, but fine with me.