RE: [Xen-devel] Disk IO scheduling in XEN

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> Hi,
> 
> We are working on a project to modify the disk scheduling mechanism in
XEN a
> bit in an attempt to improve it. In the paper "Xen and the Art of
> Virtualization"  following is mentioned.
> 
> "Xen services batches of requests from competing domains in a
> simple round-robin fashion; these are then passed to a standard
elevator
> scheduler before reaching the disk hardware"
> 
> We were going through linux-jeremy source code in an attempt to map
the above
> in code. We could not however do so. On the contrary we came to the
conclusion
> that there is no such mechanism. Domain 0 services requests as soon as
it
> receives a hypercall from a guest domain. Are we right?
> 
> Which one would be better first come first serve or round robin and
why?
> 

There was a discussion about this recently. It turns out that one DomU
can starve the others and there are real life examples of this
happening. Patches have been proposed and posted but I don't know into
what trees.

James

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