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    SubjectRe: [PATCH] tracing, perf: add more power related events

    * Thomas Renninger <trenn@suse.de> wrote:

    > On Friday 03 September 2010 21:55:55 Ingo Molnar wrote:
    > >
    > > * Thomas Renninger <trenn@suse.de> wrote:
    > >
    > > > Hi Jean,
    > > >
    > > > Summary at the beginning if people stop reading on the details
    > > > below...:
    > > > Nice work!
    > > > You have my vote to get this merged.
    > > > I think it's up to Ingo to push it.
    > >
    > > Well, the patch that got posted:
    > >
    > > [PATCH] tracing, perf: add more power related events
    > >
    > > Only adds tracepoints to power.h, but doesnt actually use them anywhere
    > > ...
    > >
    > > Is there a companion patch i missed?
    > Yep.
    > Jean has nicely made up a tiny website he refered to in his mail:
    > http://www.omappedia.com/wiki/Power_Management_Debug_and_Profiling

    Ah, that wasnt in the first patch. (Please re-start discussion threads
    when something is re-submitted)

    Nice website. Looks like these new tracepoints are really useful.

    > There he shows the whole big patch and states:

    Generally it's nice to post patches to lkml too, so that people have
    something to discuss.

    > Since the patch touches generic files (in include/trace/events/power.h), it is split in parts:
    > * generic code: submitted to the LKML, cf. http://marc.info/?l=linux-kernel&m=128195697205096&w=4 ,
    > * ARM/OMAP specific code for the already existing events: to be submitted to l-o, cf. http://www.spinics.net/lists/linux-omap/msg35357.html,
    > * ARM/OMAP specific code for the new events, to be submitted once the generic code is accepted.
    >
    > > Also, it would be nice to add it to x86 and to OMAP at once, and
    > > synchronize up all the power events
    >
    > I can add sleep state events to x86 acpi parts, but even these are, as
    > said, not that interesting as they might be on ARM ultra mobile use
    > cases.

    Yeah - but as long as they are at least attempted to be cross-platform,
    that would be fine. The ACPI folks are Cc:-ed so they can object if they
    dont like something.

    > > - and check how existing tools like
    > > powertop make use of such events - and sync it all up.
    >
    > Does powertop use these events?

    It certainly does quite a few things wrt. power usage analysis. Arjan is
    on the Cc:, maybe he has an opinion about these tracepoints.

    > > We dont want to have inconsistent, architecture-dependent events in
    > > the end, for obvious reasons.
    >
    > Jean also shows screenshots at the link above
    > how perf timechart or the the corresponding
    > gui app PyTimechart still works together with these.
    > I can't see how the new events should break an existing app, they should
    > just ignore events they are not aware of.

    Yeah, extensions rarely break anything. What i mentioned was
    'inconsistent, architecture-dependent events', which is not a fact but a
    possible danger: as these new events are only for OMAP right now. They
    might be OK, they might be not OK - i dont know, that's why i suggested
    to make them cross-platform in practice too.

    So it would be nice to get some feedback from the ACPI folks - but if
    you guys can also do an ACPI patch that would be even better!

    Thanks,

    Ingo


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