Patch for tracing c states (power_end) on x86
Robert Schöne
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);
}
/* 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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Li Zefan
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.
Robert Schöne
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.
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
------------------------- 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.
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 --------------------
Robert Schöne
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.
Am Mittwoch, den 24.02.2010, 17:00 +0800 schrieb Li Zefan:
> Robert Schöne 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.
--
Robert Schoene
Technische Universitaet Dresden
Zentrum fuer Informationsdienste und Hochleistungsrechnen
01062 Dresden
Tel.: (0351) 463-42483, Fax: (0351) 463-37773
E-Mail: Robert....@tu-dresden.de
Li Zefan
> 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,
Peter Zijlstra
> 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)
Arjan, any comments?, you seem skilled with this power stuff ;-)
Robert Schöne
I still received no reply.
--
Robert Schoene
Technische Universitaet Dresden
Zentrum fuer Informationsdienste und Hochleistungsrechnen
01062 Dresden
Tel.: (0351) 463-42483, Fax: (0351) 463-37773
E-Mail: Robert....@tu-dresden.de
--
Peter Zijlstra
> Did anyone look at the problem described and checked the patch?
> I still received no reply.
Ingo, how about applying it and letting people complain when they don't
agree? :-)
Ingo Molnar
* Peter Zijlstra <pet...@infradead.org> wrote:
> On Thu, 2010-03-11 at 07:36 +0100, Robert Sch??ne wrote:
> > Did anyone look at the problem described and checked the patch?
> > I still received no reply.
>
> Ingo, how about applying it and letting people complain when they don't
> agree? :-)
We can do that. Robert, mind sending the patch with a changelog and with your
Signed-off-by and with Peter's Acked-by?
Thanks,
Ingo