Re: [Xen-devel] poor domU VBD performance.

[Philip R Auld <pauld@xxxxxxxxxxx>]

Rumor has it that on Thu, Mar 31, 2005 at 05:34:49PM +0200 Kurt Garloff said:
> Hi,
> 
> On Thu, Mar 31, 2005 at 09:33:12AM -0500, Philip R Auld wrote:
> > This effects merging though, right? I don't think the the front
> > end has done any merging. 
> 
> The noop elevator does front and back merging.
> My understanding is that it's used in the frontend driver.

If that is the case, it can only merge things that are 
machine contiguous. Current guests know this mapping, but 
can they get this when running unmodified with VT-x.

My experience showed very little if any multipage 
IO coming out of the front end.

> 
> Otherwise, unplugging on every block would indeed be quite bad ...

Seems to be somewhat moot anyway given the curent change planned :)

Cheers,

Phil
> 
> Regards,
> -- 
> Kurt Garloff, Director SUSE Labs, Novell Inc.



-- 
Philip R. Auld, Ph.D.                          Egenera, Inc.    
Software Architect                            165 Forest St.
(508) 858-2628                            Marlboro, MA 01752

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