Re: [Xen-devel] A clocksource question

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 03/12/2010 01:56 PM, Tobias Geiger wrote:
> kbpc2:~# cat 
> /sys/devices/system/clocksource/clocksource0/current_clocksource
> xen
> kbpc2:~# cat
> /sys/devices/system/clocksource/clocksource0/available_clocksource
> xen
> kbpc2:~# echo "jiffies"
>    
> > /sys/devices/system/clocksource/clocksource0/current_clocksource
> >      
> kbpc2:~# dmesg  | tail -1
> [ 7898.642404] Override clocksource jiffies is not HRT compatible. Cannot switch
> while in HRT/NOHZ mode
> kbpc2:~#
>
> Seems like it's not possible to switch to jiffies - however:
> kbpc2:~# zcat /proc/config.gz | grep NO_HZ
> # CONFIG_NO_HZ is not set
>
> but CONFIG_SCHED_HRTICK=y
>    
Interesting.  BTW, does NO_HZ change the behaviour of this?  In 
principle NO_HZ should be preferable, and particularly in a virtual 
machine since it should limit the number of timer interrupts.
Joanna, are you using NO_HZ?

Thanks,
    J

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