Re: [PATCH] Add I/O hypercalls for i386 paravirt

[Zachary Amsden <zach@vmware.com>]

Benjamin Herrenschmidt wrote:
> On Wed, 2007-08-22 at 16:25 +1000, Rusty Russell wrote:
>   
>> On Wed, 2007-08-22 at 08:34 +0300, Avi Kivity wrote:
>>     
>>> Zachary Amsden wrote:
>>>       
>>>> This patch provides hypercalls for the i386 port I/O instructions,
>>>> which vastly helps guests which use native-style drivers.  For certain
>>>> VMI workloads, this provides a performance boost of up to 30%.  We
>>>> expect KVM and lguest to be able to achieve similar gains on I/O
>>>> intensive workloads.
>>>>         
>>> Won't these workloads be better off using paravirtualized drivers? 
>>> i.e., do the native drivers with paravirt I/O instructions get anywhere
>>> near the performance of paravirt drivers?
>>>       
>> This patch also means I can kill off the emulation code in
>> drivers/lguest/core.c, which is a real relief.
>>     
>
> Hrm... how do you deal with X doing IOs ?
>
> Ben.
>   

We have an X driver that does minimal performance costing operations.  
As we should and will have for our other drivers.

Zach