From: Sudeep Holla <sudeep.holla@arm.com>
To: Lukasz Luba <lukasz.luba@arm.com>
Cc: linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com,
vincent.guittot@linaro.org, gregkh@linuxfoundation.org,
rafael@kernel.org, rostedt@goodmis.org, mingo@redhat.com,
Sudeep Holla <sudeep.holla@arm.com>
Subject: Re: [PATCH v4] arch_topology: Trace the update thermal pressure
Date: Thu, 5 May 2022 10:16:56 +0100 [thread overview]
Message-ID: <20220505091656.2ryeyy5c7wy73uqh@bogus> (raw)
In-Reply-To: <20220427080806.1906-1-lukasz.luba@arm.com>
On Wed, Apr 27, 2022 at 09:08:06AM +0100, Lukasz Luba wrote:
> Add trace event to capture the moment of the call for updating the thermal
> pressure value. It's helpful to investigate how often those events occur
> in a system dealing with throttling. This trace event is needed since the
> old 'cdev_update' might not be used by some drivers.
>
> The old 'cdev_update' trace event only provides a cooling state
> value: [0, n]. That state value then needs additional tools to translate
> it: state -> freq -> capacity -> thermal pressure. This new trace event
> just stores proper thermal pressure value in the trace buffer, no need
> for additional logic. This is helpful for cooperation when someone can
> simply sends to the list the trace buffer output from the platform (no
> need from additional information from other subsystems).
>
> There are also platforms which due to some design reasons don't use
> cooling devices and thus don't trigger old 'cdev_update' trace event.
> They are also important and measuring latency for the thermal signal
> raising/decaying characteristics is in scope. This new trace event
> would cover them as well.
>
> We already have a trace point 'pelt_thermal_tp' which after a change to
> trace event can be paired with this new 'thermal_pressure_update' and
> derive more insight what is going on in the system under thermal pressure
> (and why).
>
Sorry for missing this, looks good to me.
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
--
Regards,
Sudeep
prev parent reply other threads:[~2022-05-05 9:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-27 8:08 [PATCH v4] arch_topology: Trace the update thermal pressure Lukasz Luba
2022-04-27 9:20 ` Greg KH
2022-04-27 9:21 ` Lukasz Luba
2022-05-05 9:16 ` Sudeep Holla [this message]
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