Re: [Xen-devel] Poor HVM performance with 8 vcpus

To:	Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] Poor HVM performance with 8 vcpus
From:	Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Date:	Wed, 07 Oct 2009 10:31:05 +0200
Cc:	James Harper <james.harper@xxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date:	Wed, 07 Oct 2009 01:31:32 -0700
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Ian Pratt wrote:
>  
>> Are there any other of these heuristics tucked away in xen? Would there
>> be any benefit to specifying the OS being virtualised in the config? Eg
>> "os=windows"?
> 
> That's really the only one that springs to mind.
> 
> Given how simple a predictor would be, I think that's the best approach.
> 
> Setting the OS in the config file is a little tricky as in a couple of 
> instances you'd want to know the exact version (linux moved the 64b direct 
> mapped region at some point during 2.6 development).

I think it is a bad idea in most cases to use such a basic parameter like
"os=xyz" to tune some specific behaviour. It may be useful to set some default
parameters, but there should be an explicit parameter as well, e.g.
"shadow_heuristic=direct-mapped@address"


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 636 47950
Fujitsu Technolgy Solutions               e-mail: juergen.gross@xxxxxxxxxxxxxx
Otto-Hahn-Ring 6                        Internet: ts.fujitsu.com
D-81739 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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Re: [Xen-devel] Poor HVM performance with 8 vcpus