Re: Reading EeePC900 battery info causes stalls

[Sitsofe Wheeler]

Steven Rostedt wrote:
> On Sat, 20 Sep 2008, Sitsofe Wheeler wrote:
>
> > Steven Rostedt wrote:
> > > OK, that is probably the known bug you are hitting. Simply disable the
> > > CONFIG_FTRACE_STARTUP_TEST and you should have the wakeup tracer. The bug is
> > > with the test, not the tracer, so it should not hurt you.
> > Thanks - this made the wakeup tracer appear a you said. I have put two wakeup
> > traces up:
> >
> > http://sucs.org/~sits/test/eeepc-debug/20080920/latency_trace.txt.gz
> > http://sucs.org/~sits/test/eeepc-debug/20080920/trace.txt.gz
> > (each file is around 6Mbytes uncompressed)
> >
> > Here's a small extract of latency_trace.txt:
> >
> > > # tracer: wakeup
> > > #
> > > wakeup latency trace v1.1.5 on 2.6.27-rc6skw-dirty
> > > --------------------------------------------------------------------
> > >  latency: 3232905 us, #65620/6180619, CPU#0 | (M:desktop VP:0, KP:0, SP:0
>
> Peter, these times are crazy, mainly due to the cpu_clock. He probably 
> wants to use the sched_clock. Below is a patch to use it instead.
>
> Sitsofe, I notice that the trace states "desktop". This means that you
> are running with CONFIG_PREEMPT_VOLUNTARY. You want 
> CONFIG_PREEMPT.
>
> [...]
> > Is it intentional that the last event has a time earlier closer to that of the
> > first event?
>
> Change the config, and see what you get with this patch:
>
> Note this is not compiled tested:

OK I've made the changes you suggested. Without preempt enabled the last 
event will have a stamp closer to the first event and the times are very 
high. With preempt enabled that beahviour has gone. Here are results 
with preempt enabled:

latency: 19657 us, #3268/3268, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0):
http://sucs.org/~sits/test/eeepc-debug/20080922/preempt/ath5k/latency_trace.txt 


latency: 104 us, #182/182, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0)
http://sucs.org/~sits/test/eeepc-debug/20080922/preempt/unplug/latency_trace.txt

latency: 95 us, #134/134, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0):
http://sucs.org/~sits/test/eeepc-debug/20080922/preempt/acpi/latency_trace.txt

latency: 91 us, #152/152, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0)
http://sucs.org/~sits/test/eeepc-debug/20080922/preempt/touchpad/latency_trace.txt

Are these the type of latencies to be expected with preemption on?

--
Sitsofe | http://sucs.org/~sits/
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