Messages in this thread | | | From | Jonathan Woithe <> | Subject | Re: 2.6.14-rt21: slow-running clock | Date | Wed, 7 Dec 2005 14:55:46 +1030 (CST) |
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> > > > When running Ingo's 2.6.14-rt21 (and in fact rt kernels back to at least > > > > 2.6.13-rc days), the clock on my i915-based laptop runs slow. The degree > > > > of slowness appears directly related to how busy the machine is. If > > > > it is just sitting around doing very little the time is kept rather > > > > well. However, as soon as the load increases the RTC and system time > > > > diverge significantly. For example, running jackd for 2 minutes results > > > > in the system time loosing as much as 20 seconds compared to the CMOS RTC. > > > > Processes doing HDD I/O also seem to affect the system time similarly. > > > > > > > > Selectively disabling different timer-related kernel options does not make > > > > any difference. However, the clock seems fine under vanilla 2.6.14, > > > > suggesting an issue somewhere in the rt patches. > > > > > > Could you please send me your dmesg and the output of: > > > > > > cat /sys/devices/system/clocksource/clocksource0/* > > > > First the contents of the above /sys/ files: > > > > /sys/devices/system/clocksource/clocksource0/current_clocksource: > > c3tsc > > > > /sys/devices/system/clocksource/clocksource0/available_clocksource > > acpi_pm jiffies c3tsc pit > > Odd. I'm not sure why the acpi_pm wasn't chosen by default if it was > available and the TSC fell back to the c3tsc. It might be something in > the -RT tree that's changed that bit. Could you try the following and > see if it doesn't resolve the timekeeping problems you're seeing? > > echo "acpi_pm" > /sys/devices/system/clocksource/clocksource0/current_clocksource
Will test it tonight.
> Still it sounds like something isn't right w/ either the c3tsc code or > the cpufreq notification code. Would you be willing to test further > patches?
Yes, no problem.
> Also could you try booting w/ idle=poll and see if that changes the > behavior?
Again, it will be done tonight and I'll advise tomorrow.
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