linux-kernel - Re: [RFC PATCH 0/3] generic hypercall support

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Message-ID: <4A043E89.90403@novell.com>
Date:	Fri, 08 May 2009 10:15:37 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Chris Wright <chrisw@...s-sol.org>,
	Gregory Haskins <gregory.haskins@...il.com>,
	Avi Kivity <avi@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, Anthony Liguori <anthony@...emonkey.ws>
Subject: Re: [RFC PATCH 0/3] generic hypercall support

Marcelo Tosatti wrote:
> On Thu, May 07, 2009 at 01:03:45PM -0400, Gregory Haskins wrote:
>   
>> Chris Wright wrote:
>>     
>>> * Gregory Haskins (ghaskins@...ell.com) wrote:
>>>   
>>>       
>>>> Chris Wright wrote:
>>>>     
>>>>         
>>>>> VF drivers can also have this issue (and typically use mmio).
>>>>> I at least have a better idea what your proposal is, thanks for
>>>>> explanation.  Are you able to demonstrate concrete benefit with it yet
>>>>> (improved latency numbers for example)?
>>>>>       
>>>>>           
>>>> I had a test-harness/numbers for this kind of thing, but its a bit
>>>> crufty since its from ~1.5 years ago.  I will dig it up, update it, and
>>>> generate/post new numbers.
>>>>     
>>>>         
>>> That would be useful, because I keep coming back to pio and shared
>>> page(s) when think of why not to do this.  Seems I'm not alone in that.
>>>
>>> thanks,
>>> -chris
>>>   
>>>       
>> I completed the resurrection of the test and wrote up a little wiki on
>> the subject, which you can find here:
>>
>> http://developer.novell.com/wiki/index.php/WhyHypercalls
>>
>> Hopefully this answers Chris' "show me the numbers" and Anthony's "Why
>> reinvent the wheel?" questions.
>>
>> I will include this information when I publish the updated v2 series
>> with the s/hypercall/dynhc changes.
>>
>> Let me know if you have any questions.
>>     
>
> Greg,
>
> I think comparison is not entirely fair.

<snip>

FYI: I've update the test/wiki to (hopefully) address your concerns.

http://developer.novell.com/wiki/index.php/WhyHypercalls

Regards,
-Greg



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