From: Greg KH <gregkh@linuxfoundation.org>
To: Lukasz Luba <lukasz.luba@arm.com>
Cc: linux-kernel@vger.kernel.org, sudeep.holla@arm.com,
dietmar.eggemann@arm.com, vincent.guittot@linaro.org,
rafael@kernel.org, rostedt@goodmis.org, mingo@redhat.com
Subject: Re: [PATCH v4] arch_topology: Trace the update thermal pressure
Date: Wed, 27 Apr 2022 11:20:31 +0200 [thread overview]
Message-ID: <YmkK32iEJ6bVyoMU@kroah.com> (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).
>
> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Much better, thanks. I'll wait for Sudeep's comments/review before
taking it into my tree.
greg k-h
next prev parent reply other threads:[~2022-04-27 9:21 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 [this message]
2022-04-27 9:21 ` Lukasz Luba
2022-05-05 9:16 ` Sudeep Holla
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YmkK32iEJ6bVyoMU@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=lukasz.luba@arm.com \
--cc=mingo@redhat.com \
--cc=rafael@kernel.org \
--cc=rostedt@goodmis.org \
--cc=sudeep.holla@arm.com \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.