[ntp:questions] Support for "tickless" systems

Rob nomail at example.com
Wed Nov 19 20:12:32 UTC 2014


David Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> On 19/11/2014 11:56, Miroslav Lichvar wrote:
>> On Wed, Nov 19, 2014 at 10:09:42AM +0000, David Taylor wrote:
>>> In bug 2314, I reported that the jitter was always reported as 0 soon after
>>> NTP had started, and this was traced to the Linux in use on the Raspberry Pi
>>> being tickless.  Recompiling the kernel without the tickless option was a
>>> work-round, but is it possible to get jitter values with a tickless system?
>>
>> There was a problem with clock stability in the tickless mode on idle
>> systems, which should be fixed or at least significantly improved in
>> 3.17. I'm not sure how it could cause the jitter to be reported as
>> zero though.
>>
>> Can you try 3.17 or later and see if it's fixed? Also, it would be
>> interesting to know if adding nohz=off to the kernel command line
>> instead of recompiling works as a workaround too.
>
> The latest Linux for the Raspberry Pi is 3.12.32+, I'm afraid.
>
> Would the command-line you speak of be the one containing - for example 
> - console=tty1 rootfstype=ext4

Yes, but normally there are a lot more options than that.  You can edit
/boot/cmdline.txt and reboot.  But be careful that you don't put garbage
there and make the boot fail.  When that still happens you can put the
card in another system (laptop, PC via USB adapter) and edit it again.



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