Xen devel - May 2010 - recurring boot time scalability issues affecting time management

The patch titled "VT-d: prevent watchdog timer from kicking in when
initializing on systems with huge amounts of memory" submitted
yesterday, other than expected, fully fixed another late boot hang
(when Dom0 was almost fully up), i.e. apparently unrelated to issues
that may exist before Dom0 even gets started. There were no
indications of time problems in any of the logs, yet there must have
been such given that the boot hung without that change, but didn''t
with it in place.

I wonder whether the time handling code in Xen itself
shouldn''t/can''t
therefore be made more robust, or at least reliably detect this sort of
issue (from past analysis of similar problems, the platform timer is
rolling over due to there not being frequent enough invocations of
plt_overflow()) to make analysis of the problem easier.

Jan


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On 11/05/2010 07:59, "Jan Beulich" <JBeulich@novell.com> wrote:
> I wonder whether the time handling code in Xen itself
shouldn''t/can''t
> therefore be made more robust, or at least reliably detect this sort of
> issue (from past analysis of similar problems, the platform timer is
> rolling over due to there not being frequent enough invocations of
> plt_overflow()) to make analysis of the problem easier.
Something like the attached?

 -- Keir
> Jan
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel


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>>> Keir Fraser <keir.fraser@eu.citrix.com> 11.05.10 09:57
>>>
>On 11/05/2010 07:59, "Jan Beulich" <JBeulich@novell.com>
wrote:
>
>> I wonder whether the time handling code in Xen itself
shouldn''t/can''t
>> therefore be made more robust, or at least reliably detect this sort of
>> issue (from past analysis of similar problems, the platform timer is
>> rolling over due to there not being frequent enough invocations of
>> plt_overflow()) to make analysis of the problem easier.
>
>Something like the attached?
Yes, except that you probably mean __builtin_llabs() rather than
__builtin_abs().

Thanks! Jan


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On 11/05/2010 09:51, "Jan Beulich" <JBeulich@novell.com> wrote:
>>>> Keir Fraser <keir.fraser@eu.citrix.com> 11.05.10 09:57
>>>
>> On 11/05/2010 07:59, "Jan Beulich"
<JBeulich@novell.com> wrote:
>> 
>>> I wonder whether the time handling code in Xen itself
shouldn''t/can''t
>>> therefore be made more robust, or at least reliably detect this
sort of
>>> issue (from past analysis of similar problems, the platform timer
is
>>> rolling over due to there not being frequent enough invocations of
>>> plt_overflow()) to make analysis of the problem easier.
>> 
>> Something like the attached?
> 
> Yes, except that you probably mean __builtin_llabs() rather than
> __builtin_abs().
xen-unstable:21346

 -- Keir



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