Re: 2.6.14-rc4-rt1

George Anzinger
2005-10-12T23:53:42Z

Fernando Lopez-Lezcano wrote:
> On Wed, 2005-10-12 at 15:08 -0700, George Anzinger wrote:
>
>>Steven Rostedt wrote:
>>
>>>On Wed, 12 Oct 2005, Ingo Molnar wrote:
>>>
>>>
>>>
>>>>i'm not sure latency traces will uncover anything useful for this bug.
>>>>Your problems could be timer issues: timers going off too fast cause
>>>>high keyboard repeat rates, and the same goes for the screensaver. Does
>>>>'sleep 1' work as expected, or is that timing out in an "accelerated"
>>>>way too?
>>>>
>>>
>>>
>>>I usually recommend doing a 'sleep 10'. It really shows you if things are
>>>wrong. If a sleep 1 returns 2 seconds, or 0.5 seconds later it may not be
>>>detected. But a sleep 10 returning 20 seconds or 5 seconds later is
>>>obvious.
>>
>>Or maybe:
>>'time sleep 10'
>>
>>Lets the machine time it.
>
>
> My first thought was "this can't work" as I imagined the same timing
> services would be used and you would get always 10 secs or so...
>
> Ingo: I tried with PREEMPT_RCU=y and it made no difference.
>
> When the system starts to misbehave I tried 'time sleep 10' and got
> really wild results:
>
> # time sleep 10
>
> real 0m10.007s
> user 0m0.001s
> sys 0m0.003s
> # time sleep 10
>
> real 0m10.006s
> user 0m0.000s
> sys 0m0.003s
> # time sleep 10
> [the return key "autorepeated" here :-]
>
>
>
> real 0m10.006s
> user 0m0.001s
> sys 0m0.003s
> #
> #
> #
> # time sleep 10
>
> real 0m0.016s
> user 0m0.002s
> sys 0m0.001s
> [yes I really got the prompt back that fast!]
> #
> #
> # time sleep 10
>
> real 73m18.087s
> user 0m0.000s
> sys 0m0.003s
> [this last one was also very fast, it did not take 73 minutes...]

Uh... this implies that your system clock is not keeping very good time. Is that so? Try:
date
time sleep 10
date

~
--
George Anzinger george@mvista.com
HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/