Re: [Xen-devel] pvops domu soft lockup under load (more logs)

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 04/16/2010 12:37 AM, Pim van Riezen wrote:
> Another datapoint. This customer has similarly loaded VPS machines on a 
> number of different hardware nodes. Not all of them had the lockup problem. I 
> applied the jiffies clocksource to all his machines, regardless of their 
> current problem status.

Does the host hardware differ?  Are they multisocket?  Intel?  AMD?

>  After a day without lockups, the customer complained about time drift (ntp 
> was not activated). The guest that had experienced the soft lockups earlier 
> had major clock drift and were way ahead:
>
>       16 Apr 09:29:26 ntpdate[11236]: step time server 194.109.22.18 offset 
> -7337.731686 sec 
>
> That's over 2 hours accumulated in less than 24 hours of uptime. The guests 
> that hadn't been excperiencing the lockup issues berfore switching to the 
> jiffies clocksource hadn't drifted that much after the switch and were, at 
> most, 120s behind after the same amount of runtime.
>   

Jiffies is a horrible clocksource.  Its accuracy is highly dependent on
the how busy the host is (not just a given guest).

    J

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