Re: [Xen-devel] Question Also regarding interrupt balancing

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 22 May 2006, at 17:43, harish wrote:

> Hi,
>  Was doing some netperf tests and noticed that all the interrupts (for 
> network) were being serviced by pcp0 although dom0 was configured to 
> use all the pcpus [4vcpus].
>  Questions:
>  1) Is there a way dom0 can be configured to process the interrupts 
> using 4pcpus instead of just one?
Running irqbalance daemon in dom0 should do the trick. If there's no 
other load in domain0 though, irqbalance may decide not to change irq 
affinity. There's no way to do fine-grained interrupt balancing (e.g., 
round-robin interrupts).
>  2) What is the recommended scheduling policy for a network I/O 
> intensive workload?
If delivering to a domU, you want dom0 and domU running on different 
CPUs or CPU will be the bottleneck.
 -- Keir

>  Sample output:
>
>  cat /proc/xen/interrupts
>
>   cat /proc/interrupts
>             CPU0       CPU1       CPU2       CPU3
>    1:          8          0          0          0        Phys-irq  
> i8042
>    8:          1          0          0          0        Phys-irq  rtc
>    9:          0          0          0          0        Phys-irq  acpi
>   11:          0          0          0          0        Phys-irq  
> ohci_hcd:usb1
>   12:        105          0          0          0        Phys-irq  
> i8042
>   14:     302432          0          0          0        Phys-irq  ide0
>   16:        375          0          0          0        Phys-irq  
> aic7xxx
>   17:      34719          0          0          0        Phys-irq  
> cciss0
>   18:      53158          0          0          0        Phys-irq  eth0
>   19:          2          0          0          0        Phys-irq  
> peth1
>   20:    1062076          0          0          0        Phys-irq  
> peth2   <<< --------Was using this
>   21:      25189          0          0          0        Phys-irq  
> peth3
>   22:      18846          0          0          0        Phys-irq  
> peth4
>   23:      18682          0          0          0        Phys-irq  eth5
>  256:    1456444          0          0          0     Dynamic-irq  
> timer0
>  257:      52873          0          0          0     Dynamic-irq  
> resched0
>  258:        282          0          0          0     Dynamic-irq  
> callfunc0
>  259:          0       7935          0          0     Dynamic-irq  
> resched1
>  260:          0      33665          0          0     Dynamic-irq  
> callfunc1
>  261:          0     508258          0          0     Dynamic-irq  
> timer1
>  262:          0          0       3827          0     Dynamic-irq  
> resched2
>  263:          0          0      33835          0     Dynamic-irq  
> callfunc2
>  264:          0          0     390316          0     Dynamic-irq  
> timer2
>  265:          0          0          0      43953     Dynamic-irq  
> resched3
>  266:          0          0          0      33870     Dynamic-irq  
> callfunc3
>  267:          0          0          0     311447     Dynamic-irq  
> timer3
>  268:       5091          0          0          0     Dynamic-irq  
> xenbus
>  269:          0          0          0          0     Dynamic-irq  
> console
>  270:      31532          0          0          0     Dynamic-irq  
> blkif-backend
>  271:    1107498          0          0          0     Dynamic-irq  
> vif7.0
>  NMI:          0          0          0          0
>  LOC:          0          0          0          0
>  ERR:          0
>  MIS:          0
>
>  Ran multiple while loops to confirm that dom0 can use all the 4pcpus 
> if required. And so believe it must be something to do with the way 
> the interrupts are being handled.
>  Thanks in advance,
>  hmv
>
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