Messages in this thread | | | Date | Mon, 17 Aug 2009 19:46:49 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: clocksource changes in 2.6.31 - possible regression |
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On Mon, 17 Aug 2009, Stephen Hemminger wrote: > The following commit causes a change for kernels built with HRT but > not actually using HRT. I typically use the generic kernel we ship > on test machines, and that kernel has NOHZ and HRT (for power savings/virt > and HRT for QoS), but I want to be able to enable TSC as a clock source > when doing performance tests with pktgen. > > The machine in question is a several year old Opteron box, that > normally reports clocksources: acpi_pm jiffies tsc > but now with 2.6.31-rc6, it only has acpi_pm. > > Since HRT/NOHZ is not really runtime configurable, I think the > proper behavior is:
Isn't highres=off resp. nohz=off on the kernel command line not good enough ?
> * kernel reports all possible clocksources and chooses the best > by default > * if user demands a different clocksource, the kernel should use that > but degrade if necessary: ie. high-res timers have less (maybe even > only HZ accuracy), and nohz should be automatically disabled if > needed
We never implemented to back out from highres/nohz and I have no urge to do so :)
Thanks,
tglx
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