[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Question regarding Xen scheduler

On 08/10/14 14:05, Zytaruk, Kelly wrote:
> I would like to ask a question as to how the Xen scheduler handles certain 
> situations.  
> From everything that I have read I understand that the scheduler treats Dom0 
> just like any other DomU in regards to scheduling.

Correct.  (XenServer has a tweak which allows dom0's credit to scale
relative to current system load, but nothing more complicated.)

> My question is in regards to interrupt handlers, critical sections and kernel 
> code.  Is the Xen scheduler aware of whether the Dom0 is executing in kernel 
> code versus user mode code?  Can Dom0 kernel mode code be interrupted by the 
> Xen scheduler and then a DomU run for a while before returning back to Dom0 
> kernel mode code?

All domains may be interrupted by Xen.  Xen itself knows whether the
domain is in kernel or user mode, but the scheduler does not. 

> What about interrupt handling routines either in Dom0 or DomU.  Can a Task 
> switch to another DomU / Dom0 occur if in the middle of an interrupt handler?


> What if I am doing something time critical or sequence critical that can't be 
> interrupted?  Is there a way to tell the Xen scheduler that "I am in a 
> critical section and can't be interrupted by another Dom" so that Xen won't 
> task switch until I am done?


> Other than reading the source code is there a good reference that I can read 
> for Xen internal details and architecture?  

Not which comes to mind.


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.