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

[Philip R Auld <pauld@xxxxxxxxxxx>]

Rumor has it that on Thu, Mar 31, 2005 at 08:01:52PM +0200 Jens Axboe said:
> On Thu, Mar 31 2005, Philip R Auld wrote:
> > 
> > My experience showed very little if any multipage 
> > IO coming out of the front end.
> 
> There aren't that many users of multipage ios yet. direct io will use
> it, ext2 will as well. iirc, -mm has patches for ext3 too. so it's
> definitely improving :-)

Sorry, I was being sloppy with terminology :)

What I was getting at was that the backend  will split requests
up and issue each physical segment as a separate bio  (at least in 
the 2.0.5 tree I have in front of me). And that none of these 
physical segments was more that 1 page. 

So the request merging in the back end OS is important, no?


Cheers,

Phil

> 
> -- 
> Jens Axboe

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

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