Re: [Xen-devel] PV drivers for HVM guests

["Ky Srinivasan" <ksrinivasan@xxxxxxxxxx>]

Andrew,

The I/O performance of HVM guests with PV drivers is SIGNIFICANTLY better than 
what we get without PV drivers. I will post the patches after some additional 
testing and code cleanup.

Regards,

K. Y

>>> On Tue, Oct 3, 2006 at  6:19 PM, in message
<1159913996.27206.37.camel@localhost>, "Andrew D. Ball" <aball@xxxxxxxxxx>
wrote: 
> Interesting!  Ideally, there would be better performance in the base HVM
> device model.  I think I know of some people that are working hard on
> that.
> 
> I'm curious to see what you've done for (1) and (2).
> 
> Peace.
> Andrew
> 
> On Tue, 2006-  10-  03 at 16:31 -  0400, Ky Srinivasan wrote:
>> I am trying to build PV drivers for SLES9 HVM guests. SLES 9 is based on the 
> 2.6.5 kernel. Since the PV driver code is really designed for the latest 
> kernel release, I have had many issues/problems in building the PV drivers 
> for older Linux OS targets -   I have only been looking at the issues with 
> 2.6.5 
> kernel base and I suspect the problem will be even worse if one were to look 
> at older Linux kernels. This is unfortunate since PV drivers are so critical 
> for HVM guests and there is considerable interest in supporting legacy Linux 
> environments as HVM guests. The problems I have had to deal with can be 
> broadly classified into:
>> 
>> a) Compiler related issues
>> b) Missing functionality in the legacy kernel -   this includes features as 
> well as changed data structures
>> c) Implementation differences of a given feature
>> 
>> These differences can be dealt with in a couple of different ways:
>> 1) Modify the code in the PV drivers under appropriate compilation switches 
> to deal with the differences in the base kernels.
>> 2)  Introduce  a compatibility component that bridges the gap between the 
> current PV code and a given Linux target and leave much of the PV driver  
> code untouched.
>> 
>> I have implemented both these schemes for the sles9 kernel and would like to 
> get your input on your preference. I personally like option 2. Going forward, 
> the evolution of PV drivers needs to be constrained by the required support 
> for legacy Linux environments. 
>> 
>> Regards,
>> 
>> K. Y. Srinivasan 
>> 
>> 
>> 
>> 
>> 
>> _______________________________________________
>> 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



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel