Re: [timer/ticks related] dom0 hang during boot on large 1TB system

[Jeremy Fitzhardinge <jeremy@goop.org>]

On 12/21/2009 11:52 AM, Mukesh Rathor wrote:
> On Mon, 21 Dec 2009 19:07:39 +0000
> Keir Fraser<keir.fraser@eu.citrix.com>  wrote:
>
>    
>> On 21/12/2009 18:20, "Dan Magenheimer"<dan.magenheimer@oracle.com>
>> wrote:
>>
>>      
>>> Not to say the problem can't or shouldn't be fixed in Xen.
>>> Keir, would bad things happen if construct_dom0 is done after
>>> scrub_heap_pages()?  Other than some time wastage because
>>> dom0's memory would get scrubbed just before it gets
>>> overwritten (which is admittedly a much bigger problem
>>> when dom0_mem is not specified in the Xen boot line
>>> on a machine with ginormous memory).
>>>        
>> The problem is more likely that Xen system time started ticking some
>> time earlier during boot process. I doubt it is to do with ordering of
>> construct_dom0 versus boot-time scrubbing.
>>
>>   -- Keir
>>
>>      
> The problem is exactly how Dan described it. 'delta' for first interrupt
> in dom0->timer_interrupt() goes up proportionately with amount of memory
> on system. On this box, it appears more than 600GB causes delta to be
> large enough to wrap jiffies.
>
>   1TB delta: 940b7d68a4
> 32GB delta: 02ae56eadb
>
> xen->send_guest_vcpu_virq() ---->  dom0->handle_IRQ() ->  timer_interrupt()
>
> timer_interrupt will call do_timer delta/NS_PER_TICK number of times.
>    

How is it computing that delta?

Anyway, I'm not at all sure this will apply to a pvops dom0 kernel as it 
does timekeeping quite differently from 2.6.18-xen.

     J