Interrupts in Xen: Dynamic-irq and Phys-irq

Interrupts in Xen: Dynamic-irq and Phys-irq

[John Que]

Hello, 
  I am running the xen-unstable (linux 2.6.11 kernel) after building
it from source.

I had noticed that , when starting a new domain, and running:

cat /proc/interrupts, it show many irq which are of type "Dynamic-irq":

for example:
.....
259:        234     Dynamic-irq  blkif
.....

I had traced down it down in xen source  to dynirq_type struct in: 
linux-2.6.11-xen-sparse/arch/xen/kernel/evtchn.c:

static struct hw_interrupt_type dynirq_type = 
  {
  "Dynamic-irq",
  startup_dynirq,
  shutdown_dynirq,
  enable_dynirq,
	...
	...
	};
	
 I saw a usage of this struct (might it be the only usage ?) 
 in the init_IRQ() method, in this evtchn.c:
  ......
 irq_desc[dynirq_to_irq(i)].handler = &dynirq_type; 
 .......
 
 irq_desc is an instance irq_desc struct (in irq.h) ; 
 It's  handler member is a pointer to hw_irq_controller, which is in fact 
 hw_irq_controller.  

 ( in irq.h .there is a "typedef struct hw_interrupt_type  hw_irq_controller");
 
 Does anybody know and can explain in few sentences what is this Dynamic-irq? 
 What is it's use? 
 
 The "Dynamic-irq" also appears in Dom0 (for example, when you run 
"cat /proc/interrupts" and look at the  line containing "ctrl-if" or "console").

Besides it, In dom0 there is also "Phys-irq" ; for examples,after 
running "cat /proc/interruupts" in line containing "eth0" or "ide0" or "ide1". 

what is the difference between these 2 types of interrupts ? 

 Regards,
John Q.

Re: Interrupts in Xen: Dynamic-irq and Phys-irq

[Keir Fraser]

On 18 Jul 2005, at 13:07, John Que wrote:

> The "Dynamic-irq" also appears in Dom0 (for example, when you run
> "cat /proc/interrupts" and look at the  line containing "ctrl-if" or 
> "console").
>
> Besides it, In dom0 there is also "Phys-irq" ; for examples,after
> running "cat /proc/interruupts" in line containing "eth0" or "ide0" or 
> "ide1".
>
> what is the difference between these 2 types of interrupts ?

Phys-irq's relate directly to hardware IRQ lines (e.g., eth0, your disc 
controller, etc). Dynamic-irq's are perhaps better described as 
'virtual IRQs'. They have no direct relation to physical IRQ lines, but 
originate from things like timer events in Xen, or from the other half 
of a 'split' virtual block or network driver. We call them 'dynamic 
IRQs' because the IRQ numbers are dynamically allocated. :-)

  -- Keir

Re: Interrupts in Xen: Dynamic-irq and Phys-irq

[John Que]

Hello, 

Thanks!
Your answer makes things more understandable.

Regards,
John 

On 7/18/05, Keir Fraser <Keir.Fraser@cl.cam.ac.uk> wrote:
> 
> On 18 Jul 2005, at 13:07, John Que wrote:
> 
> > The "Dynamic-irq" also appears in Dom0 (for example, when you run
> > "cat /proc/interrupts" and look at the  line containing "ctrl-if" or
> > "console").
> >
> > Besides it, In dom0 there is also "Phys-irq" ; for examples,after
> > running "cat /proc/interruupts" in line containing "eth0" or "ide0" or
> > "ide1".
> >
> > what is the difference between these 2 types of interrupts ?
> 
> Phys-irq's relate directly to hardware IRQ lines (e.g., eth0, your disc
> controller, etc). Dynamic-irq's are perhaps better described as
> 'virtual IRQs'. They have no direct relation to physical IRQ lines, but
> originate from things like timer events in Xen, or from the other half
> of a 'split' virtual block or network driver. We call them 'dynamic
> IRQs' because the IRQ numbers are dynamically allocated. :-)
> 
>   -- Keir
> 
>