[CentOS-virt] tick divider bugs

Sat May 3 19:57:57 UTC 2008
Allen Tsang <atsang at advance.net>

Also just to review, clocksource=acpi_pm should be used in conjunction 
with the tools.synctime = "true" flag in your vmx file.  The combination 
of the two settings prevents time from going into the future from too 
many ticks, and synctime corrects slow clocks, which leads to a much, 
much better clock sync.

We'll have to wait until someone figures out a clever way to tie VM 
clock ticks to a multiplexed physical clock source;
until then, clocksync will always be a problem without a complete 
solution (read up on it).  This is as close as it gets!

Allen Tsang wrote:
> clocksource=pit is confirmed not working in VMware ESX.
> You should be using clocksource=acpi_pm in addition to divider=10 to 
> reduce idle load.
> Binding to a single CPU is hardly a fix.  Always engineer *real* 
> solutions, not poor workarounds! ;)
> Kai Schaetzl wrote:
>> Akemi Yagi wrote on Sat, 3 May 2008 06:06:31 -0700:
>>> I
>>> tried it but it seems to have the same problem as before - when used
>>> with clocksource=pit, it hangs on bootup.
>> For the record, this can also happen in other situations with VMWare. 
>> For instance, I have seen that happen with a Suse 9.0 guest on VMWare 
>> Server that is running on Win2k3. I was trying clocksource=pit 
>> because the clock was jumping ahead of time like nothing. I figured 
>> that it is actually a problem with the Suse kernel not liking that 
>> specific option (it didn't hang with other clock options). I fixed 
>> the time problem by binding the virtual machine to one CPU core. I 
>> didn't even have to shut off the power saving features of the CPU.
>> Kai
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