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

[Jens Axboe <axboe@xxxxxxx>]

On Thu, Mar 31 2005, 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.

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 :-)

-- 
Jens Axboe


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