linux-kernel - Re: [PATCH v1] PM / Domains: Add tracepoints

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20191001174235.GC87296@google.com>
Date:   Tue, 1 Oct 2019 10:42:35 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Douglas Anderson <dianders@...omium.org>,
        linux-pm@...r.kernel.org, Amit Kucheria <amit.kucheria@...aro.org>,
        linux-kernel@...r.kernel.org,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>
Subject: Re: [PATCH v1] PM / Domains: Add tracepoints

On Tue, Oct 01, 2019 at 01:03:43PM -0400, Steven Rostedt wrote:
> On Tue, 1 Oct 2019 09:35:42 -0700
> Matthias Kaehlcke <mka@...omium.org> wrote:
> 
> > How about this instead:
> > 
> >   Add tracepoints for genpd_power_on, genpd_power_off and
> >   genpd_set_performance_state. The tracepoints can help with
> >   understanding power domain behavior of a given device, which
> >   may be particularly interesting for battery powered devices
> >   and suspend/resume.
> 
> Do you have a use case example to present?

TBH I'm not looking into a specific use case right now. While
peeking around in /sys/kernel/debug/tracing/events to learn more
about existing tracepoints that might be relevant for my work
I noticed the absence of genpd ones and it seemed a good idea to
add them preemptively. Conceptually they seem similar to the
existing regulator_enable/disable and cpu_idle tracepoints.

As an abstract use case I could see power analysis on battery
powered devices during suspend. genpd_power_on/off allow to see
which power domains remain on during suspend, and might give
insights for possible power saving options. Examples could be that
a power domain stays unexpectedly on due to a misconfiguration, or
two power domains remain on when it could be only one if you just
moved that one pin/port over to the other domain in the next
hardware revision.