Re: [Xen-devel] XEN 4.0 + 2.6.31.13 pvops kernel : system crashes on starting 155th domU

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Cc'ing Ian and Jeremy -- one of them should be able to answer definitively
on this. I'm *pretty* sure there's an easy way to bump the irq limit you're
hitting, on the pv_ops kernels, but 'nr_irqs=' on dom0 cmdline clearly isn't
it as it had no effect at all!

 -- Keir

On 28/04/2010 07:47, "John McCullough" <jmccullo@xxxxxxxxxxx> wrote:

> I did a little testing.
> 
> With no kernel option:
> # dmesg | grep -i nr_irqs
> [    0.000000] nr_irqs_gsi: 88
> [    0.000000] NR_IRQS:4352 nr_irqs:256
> 
> w/nr_irqs=65536:
> # dmesg | grep -i nr_irqs
> [    0.000000] Command line: root=/dev/sda1 ro quiet console=hvc0
> nr_irqs=65536
> [    0.000000] nr_irqs_gsi: 88
> [    0.000000] Kernel command line: root=/dev/sda1 ro quiet console=hvc0
> nr_irqs=65536
> [    0.000000] NR_IRQS:4352 nr_irqs:256
> 
> tweaking the NR_IRQS macro in the kernel will change the NR_IRQS output,
> but unfortunately that doesn't change nr_irqs and I run into the same
> limit (36 domus on a less-beefy dual core machine).
> 
> I did find this:
> http://blogs.sun.com/fvdl/entry/a_million_vms
> which references NR_DYNIRQS, which is in 2.6.18, but not in the pvops
> kernel.
> 
> Watching /proc/interrupts, the domain irqs seem to be getting allocated
> from 248 downward until they hit some other limit:
> ...
>   64:      59104  xen-pirq-ioapic-level  ioc0
>   89:          1   xen-dyn-event     evtchn:xenconsoled
>   90:          1   xen-dyn-event     evtchn:xenstored
>   91:          6   xen-dyn-event     vif36.0
>   92:        140   xen-dyn-event     blkif-backend
>   93:         97   xen-dyn-event     evtchn:xenconsoled
>   94:        139   xen-dyn-event     evtchn:xenstored
>   95:          7   xen-dyn-event     vif35.0
>   96:        301   xen-dyn-event     blkif-backend
>   97:        261   xen-dyn-event     evtchn:xenconsoled
>   98:        145   xen-dyn-event     evtchn:xenstored
>   99:          7   xen-dyn-event     vif34.0
> ...
> Perhaps the xen irqs are getting allocated out of the nr_irqs pool,
> while they could be allocated from the NR_IRQS pool?
> 
> -John
> 
> 
> 
> 
> On 04/27/2010 08:45 PM, Keir Fraser wrote:
>> I think nr_irqs is specifiable on the command line on newer kernels. You may
>> be able to do nr_irqs=65536 as a kernel boot parameter, or something like
>> that, without needing to rebuild the kernel.
>> 
>>   -- Keir
>> 
>> On 28/04/2010 02:02, "Yuvraj Agarwal"<yuvraj@xxxxxxxxxxx>  wrote:
>> 
>>    
>>> Actually, I did identify the problem (don’t know the fix) at least from
>>> the console logs. Its related to running out of nr_irq's  (attached JPG
>>> for the console log).
>>> 
>>> 
>>> -----Original Message-----
>>> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>>> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
>>> Sent: Tuesday, April 27, 2010 5:44 PM
>>> To: Yuvraj Agarwal; xen-devel@xxxxxxxxxxxxxxxxxxx
>>> Subject: Re: [Xen-devel] XEN 4.0 + 2.6.31.13 pvops kernel : system crashes
>>> on starting 155th domU
>>> 
>>> On 27/04/2010 08:41, "Yuvraj Agarwal"<yuvraj@xxxxxxxxxxx>  wrote:
>>> 
>>>      
>>>> Attached is the output of /var/log/daemon.log and /var/log/xen/xend.log,
>>>>        
>>> but
>>>      
>>>> as far as we can see we don¹t quite know what might be going causing the
>>>> system to crash (no console access anymore and system becomes
>>>>        
>>> unresponsive and
>>>      
>>>> needs to be power-cycled).  I have pasted only the relevant bits of
>>>> information (the last domU that did successfully start and the next one
>>>>        
>>> that
>>>      
>>>> failed). It may be the case that all the log messages weren¹t flushed
>>>>        
>>> before
>>>      
>>>> the system crashedŠ
>>>> 
>>>> Does anyone know where this limit of 155 domU is coming from and how we
>>>>        
>>> can
>>>      
>>>> fix/increase it?
>>>>        
>>> Get a serial line on a test box, and capture Xen logging output on it. You
>>> can both see if any crash messages come from Xen when the 155th domain is
>>> created, and also try the serial debug keys (e.g., try 'h' to get help to
>>> start with) to see whether Xen itself is still alive.
>>> 
>>>   -- Keir
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-devel
>>>      
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
>>    
> 



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