Re: Patch for tracing c states (power_end) on x86

[Robert Schöne]

I forgot to mention that I appended my original mail at the bottom of my
previous one.
Here it is:
> ------------------------- Mail from Febr. 15th --------------------
> > Hi,
> > I have a question regarding the event "power/power_end".
> > For the standard linux kernel (2.6.32.8), it's just not reported -
> > neither for the /sys/kernel/debug/tracing nor for the sys_perf_open
> > approach.
Reported means here: sampling events were not generated/there were no entries in debug/tracing.
> > 
> > System:
> >         Intel Core 2 Quad,
> >         Kernel 2.6.32.8,
> >         for sys_perf_open:always using sampling counters,
> >         (Kernel 2.6.33-rcX should show the same behavior)
> > 
> > After finding "my" c-state procedure in arch/x86/kernel/process.c
> > (which was "static void mwait_idle(void)" btw), I added a
> > trace_power_end call on the correct line:
> > ...
> >                 else
> >                         local_irq_enable();
> >         } else
> > ...
> > ->
> > ...
> >                 else
> >                         local_irq_enable();
> >                 trace_power_end(0);
> >         } else
> > ...
> > Now the event was reported on /sys/kernel/debug/tracing, but still not
> > for sys_perf_open.
> > 
> > Then I had the idea, that trace_power_end's argument should be the same
> > as the 2nd argument of the previous power_start.
> > 
> > That worked.
> > 
> > However, things to be done are: add trace_power_end's to some
> > process.c's procedures.
> > 
> > 
> > Bye Robert
> > 
> > -------------------------End of Mail of Febr. 15th --------------------

Am Mittwoch, den 24.02.2010, 17:00 +0800 schrieb Li Zefan:
> Robert SchÃne wrote:
> > Hi,
> > 
> 
> Please don't top posting. :)
> 
> > I tried to pass 0 in "my" sleep routine "static void mwait_idle(void)"
> > Which led to the following behaviour:
> > The event was reported on /sys/kernel/debug/tracing, but still not
> > for sys_perf_open.
> 
> The event was not reported by sys_perf_open()? Could you be more
> elaborate on this? Because I don't get you here.
> 
> > As 1 had been the argument which led to a working tracing, I assumed,
> > that the argument should be the same as the 2nd arg of the last
> > power_start event.
> > Since this argument had been 1 in my case, it worked for me. However, 0
> > did not.
> > 
> > Bye Robert
> > 
> > 
> > 
> > Am Mittwoch, den 24.02.2010, 16:36 +0800 schrieb Li Zefan:
> >> Robert SchÃne wrote:
> >>> Hello,
> >>>
> >>> Since noone replied to my last mail (Febr. 15th, 11:42), describing the
> >>> way to fix the missing c-state tracing, here's a patch.
> >>> Maybe its easier that way.
> >>>
> >>> (I used the perf-fixes-for-linus git tree to obtain a
> >>> more-then-up-to-date version)
> >>>
> >>> Bye Robert
> >>>
> >>>
> >>> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> >>> index 02d6780..b1cfb88 100644
> >>> --- a/arch/x86/kernel/process.c
> >>> +++ b/arch/x86/kernel/process.c
> >>> @@ -384,6 +384,7 @@ void default_idle(void)
> >>>                 else
> >>>                         local_irq_enable();
> >>>                 current_thread_info()->status |= TS_POLLING;
> >>> +               trace_power_end(1);
> >>>         } else {
> >>>                 local_irq_enable();
> >>>                 /* loop is done by the caller */
> >>> @@ -451,6 +452,7 @@ void mwait_idle_with_hints(unsigned long ax,
> >>> unsigned long cx)
> >>>                 if (!need_resched())
> >>>                         __mwait(ax, cx);
> >>>         }
> >>> +       trace_power_end((ax>>4)+1);
> >> The only argument of trace_power_end() is a dummy, so you can just
> >> pass 0 or 1 to the trace hook, actually better pass 0 to be
> >> consistent with other parts.
> >>
> >> The dummy argument can't be eliminated, because the macros that
> >> automatically generates racing code have some limitations, and
> >> seems it's not so easy to get over.
> >>
> >>>  }
> >>>  
> >>>  /* Default MONITOR/MWAIT with no hints, used for default C1 state */
> >>> @@ -467,6 +469,7 @@ static void mwait_idle(void)
> >>>                         __sti_mwait(0, 0);
> >>>                 else
> >>>                         local_irq_enable();
> >>> +               trace_power_end(1);
> >>>         } else
> >>>                 local_irq_enable();
> >>>  }
> >>>
> >>>
> >> --
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> >>

> > 
> > 
> > 
> > 
> --
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> 


-- 
Robert Schoene
Technische Universitaet Dresden
Zentrum fuer Informationsdienste und Hochleistungsrechnen
01062 Dresden

Tel.: (0351) 463-42483, Fax: (0351) 463-37773
E-Mail: Robert.Schoene@xxxxxxxxxxxxx

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