[Xen-devel] Re: [PATCH] clocksource=tsc

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

My best guess is still that Xen's calculation of time is diverging from dom0
kernel's. For some reason that is unclear, since of course the calibration
info should be statically determined at boot and never change from there on.

 -- Keir

On 16/7/08 16:42, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> Nope, its not ntpd.  Everything seemed fine for at
> least 15-20 minutes, then I went away for awhile
> and when I checked back an hour later, same weird
> symptoms as before.
> 
> I also tried running with nosmp on the xen boot line
> (and confirmed that only one processor was started).
> Same results... after about an hour.  So it doesn't
> appear to be a result of cross-CPU time issues.
> 
>> From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
>> 
>> I'm thinking the problem may only occur when dom0 is
>> running ntpd.  Maybe "setting" the platform time only
>> changes one CPU, or sets the platform time differently
>> than system time?
>> 
>>> -----Original Message-----
>>> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
>>> Sent: Wednesday, July 16, 2008 6:50 AM
>>> To: dan.magenheimer@xxxxxxxxxx; Xen-Devel (E-mail)
>>> Cc: Dave Winchell
>>> Subject: Re: [PATCH] clocksource=tsc
>>> 
>>> 
>>> That's a weird set of symptoms. Perhaps dom0's sense of
>> system time is
>>> diverging from Xen's? I don't see that CPUs can diverge, if
>>> their TSCs are
>>> in sync, since we shouldn't be dynamically modifying the
>>> per-CPU timestamps
>>> or scale factors.
>>> 
>>>  -- Keir
>>> 
>>> On 16/7/08 13:43, "Dan Magenheimer"
>>> <dan.magenheimer@xxxxxxxxxx> wrote:
>>> 
>>>> Well now I have to take that back.  It DOESN'T work yet.
>>>> I think I am experiencing "Weirdness can happen..."
>>>> when booting with clocksource=tsc... I was away from
>>>> the machine overnight but the symptoms I've seen before
>>>> are that the system becomes less snappy and eventually
>>>> grinds to a near-halt.
>>>> 
>>>> Oddly, I can login most of the way on the console
>>>> and launch new xterm's in my VNC display, but I never
>>>> get a prompt, and I can't interrupt a process I left
>>>> running overnight in another xterm.  The time display
>>>> in gnome seems to have frozen about an hour after
>>>> I booted.  Pinging the machine works but ssh'ing to
>>>> it doesn't ("Connection closed")
> 
> 



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