On 11/04/2013 05:34 PM, Thierry Bultel wrote:
> Le 04/11/2013 17:11, Gilles Chanteperdrix a écrit :
>> On 11/04/2013 05:16 PM, Thierry Bultel wrote:
>>> Hi,
>>>
>>> My configuration is
>>> xenomai-2.6.3 + ipipe-1.18-13, freescale kernel rel_imx_3.0.35_4.0.0, on
>>> the IMX6Q.
>>>
>>> I want to use CONFIG_HIGH_RES_TIMERS and CONFIG_HZ=100, which is the
>>> default value for the IMX.
>>
>> Do you observe the same issue without CONFIG_HIGH_RES_TIMERS?
>>
>>
>
> Without CONFIG_HIGH_RES_TIMERS, the wait precision is dictated by
> CONFIG_HZ, in other words 10 ms.
>
> FYI as I needed to wait 30ms with a 1 ms precision, I formerly had to
> hack Kconfig to allow CONFIG_HZ=1000 (and it worked fine).
It appeared to work fine, however Linux is not an RTOS, it can not
guarantee a 1ms latency. Why not using Xenomai for precise sleeps? Other
than that, I have no idea, I would use the I-pipe tracer to understand
what is going on in between the time when the timer ticks and the time
when the task is woken up.
--
Gilles.
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