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On Mon, 13 Sep 2010, Simon Waters wrote:
When compiling a kernel what affects available clock sources?
Compile options and the BIOS?
Trying to resolve an issue with a virtual machine that doesn't keep good time. One workaround in the Debian Wiki is to set clocktime to "jiffies" another is to set it to "pit", this would be good if either were available to chose from.Specifically the file: /sys/devices/system/clocksource/clocksource0/available_clocksource Lacks the options I would like to use.
Does it have HPET?
I assume the content of this file varies with the kernel compilation options, the system has a bespoke kernel that claims to come from Ubuntu with vendor supplied hacks. I have a config file and a description of how the bespoke bits were added in, and suggestions on how I might use Debian stock kernels in this environment (planning to switch ASAP, but would like to understand fully clock issues before braving other things that will almost certainly be more complex).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...
Have these options been removed, or are they missing because the current settings refer to apparently inappropriate KVM or Paravirtualised clock features?
Never build a kernel for KVM, etc. so I'd not know if they get auto removed..
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.
Is there anything better than reading the source here, and if not which bit of source to start with?
Oddly enough, I've had some issues here myself - with a number of systems telling me the clocksouce has become unstable some 30 seconds afterboot... So I've no idea what the real issues are, however I switched to using HPET as a clocksource - needed:
hpet=force clocksource=hpet on the kernel boot line (append ...)(The force was for one particular VIA motherboard who's BIOS 'hides' it for some bizarre reason) however the Geodes see it from boot (as does my desktop Atom, and others) I've had HPET compiled into the kernels for a long time now as the asterisk drivers seem to prefer it.
No issues with my virtual servers, but they're all using LXC, so only one kernel to wory about.
Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq