lkml.org 
[lkml]   [2008]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: PATCH] ftrace: Add a C/P state tracer to help power optimization
    On Mon, 06 Oct 2008 22:46:09 +0200
    Andi Kleen <andi@firstfloor.org> wrote:
    > >
    > > + trace_power_mark(&it, POWER_PSTATE, next_perf_state);
    >
    > Wouldn't that be better higher up in the cpufreq system? It would
    > seem bad to duplicate that in all low level cpufreq modules.

    the problem is that higher up the actual P state isn't known.

    >
    > Also I suspect some higher level format would be good here too.
    > Just put the frequency in?

    the link between P states and frequency is... rather lose.
    Especially with Turbo Mode it no longer is really relevant to list
    frequencies.

    > > + ret = trace_seq_printf(s, "[%5ld.%09ld]
    > > CSTATE: Going to C%i on cpu %i for %ld.%09ld\n",
    > > + stamp.tv_sec,
    > > + stamp.tv_nsec,
    > > + it->state, iter->cpu,
    > > + duration.tv_sec,
    > > + duration.tv_nsec);
    > > + if (it->type == POWER_PSTATE)
    > > + ret = trace_seq_printf(s, "[%5ld.%09ld]
    > > PSTATE: Going to P%i on cpu %i\n",
    > > + stamp.tv_sec,
    > > + stamp.tv_nsec,
    > > + it->state, iter->cpu);
    >
    > I suspect a less verbose output format would be better.
    why?
    It's fine as it is, and it's actually human readable as well.

    >
    > > +{
    > > + if (!trace_power_enabled)
    > > + return;
    > > +
    > > + memset(it, 0, sizeof(struct power_trace));
    >
    > The memset seems redundant.

    it's free and it initializes the datastructure cleanly; and only when
    the tracer is in use.

    >

    > Hmm, that does a unconditional wake_up() in idle. Doesn't this cause
    > a loop on UP?
    >
    > idle -> wakeup -> idle -> wakeup -> ... etc.
    >
    > Am I missing something?

    yes you're missing something ;-)
    this code is called when going out of idle, not when going into idle.


    --
    Arjan van de Ven Intel Open Source Technology Centre
    For development, discussion and tips for power savings,
    visit http://www.lesswatts.org


    \
     
     \ /
      Last update: 2008-10-06 22:59    [W:0.033 / U:30.980 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site