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On Mon, 13 Sep 2010, Simon Waters wrote:
Gordon Henderson wrote:Does it have HPET?No only: tsc acpi_pm Neither of these sort my time problem.However for 2.6.32 kernel on AMD 64 bit processor, what affects the contents of available_clocksource?I supspect the BIOS and what's compiled into the kernel...I think I need specifics, or at least pointers to specifics. I'd have expected things like "jiffies" shouldn't be too dependent on the BIOS. I'm also not sure what CONFIG_NO_HZ does to clocks (if anything).
I'd hope the BIOS didn't have any effect, but I can't work out why the BIOS on this particular motherboard 'hides' the HPET device (maybe just lazy to not initialise it though)
CONFIG_NO_HZ shouldn't do anything (other than save some power) - at least I don't notice it on the systems I comfigure it in - however it's not much use when they're taking 1000 interrupts a second via HPET or telephony hardware...
Never build a kernel for KVM, etc. so I'd not know if they get auto removed..This is XEN I just noted the KVM clock config setting was enabled (CONFIG_KVM_CLOCK), I suspect it is irrelevant but I figured I'd mention it because I don't know it is irrelevant.I noted that adding a second CPU to a domU loses the "tsc" clock source, which makes sense.Come to think of it, I'm not sure I've actually seen any kernel options to actively specify the clocksource at build time - however you can set it at boot time.I have no problem setting it, I believe the default is tsc, you can of course use "clock=" or /etc/sysctl.conf to set it after boot, which is early enough in the process that I don't care if we are a few seconds out at boot as long as at some point before starting mail software it gets the correct and stable time from somewhere (Host, NTP, I'm not choosy).
I think you ought to be using clocksource= in 2.6.3x kernels, clock= has been deprecated somewhat...
Time of day is set very early on in the boot process - usually from the hardware clock, then possibly from ntpdate and ntp. I do have some boards without an on-board battery, so I had to modify things somewhat to get the date from tinternet right after the network comes up. (Not always successfull as my PBXs start faster than some ADSL routers do!)
I just don't have the values I want to set it to, and I figured I'd ask here before braving recompiling bits of the kernel I don't understand in any meaningful way, as I'm sure after a dozen or so tweaks I'll understand it better and get something that works, but it would be nice to get there is (a) one step (b) with confidence it was the right thing to do.
What do you want to set it to? (Although I'd guess whatever Xen prefers it set to ;-)
If you've got a .config, then a re-compile ought to be straightforward. What have you got to lose ;-)
Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq