RE: [Xen-devel] Real-time support

["Ky Srinivasan" <ksrinivasan@xxxxxxxxxx>]

>>> On Tue, May 8, 2007 at  4:56 PM, in message
<8A87A9A84C201449A0C56B728ACF491E0BA4E3@xxxxxxxxxxxxxxxxxxxxxxxxxxx>, "Ian
Pratt" <Ian.Pratt@xxxxxxxxxxxx> wrote: 
>>  I did some basic measurements on worst case execution time inside the
>> hypervisor a while ago (6- 8 months ago).  From what i remember, the
>> worst case where between 1- 2msec on a 3GHz P4.  This was under some
>> load (make - j64 bzImage).  A big culprit was the mmu- ext hypercall
>> which in certain cases recursively unpins a page table. Handling
>> certain page faults also took a while. This was just a preliminary
>> study so i didn't push the analysis very far.
> 
> The pin/unpin operations are certainly by far the longest running
> operations in Xen, and it's been on the to- do list to make them
> preemptable for a long time. This should be very simple as we can exit
> the hypervisor leaving the EIP on the hypercall, and next time the guest
> calls in we'll pick up where we left off. 
> 
> Anyone who cares about real time on x86 up for implementing this?

Thanks Ian. We would be interested in looking at this.

Regards,

K. Y 




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