Re: [Xen-devel] system load

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> Where does system load live for xen related tasks?
> If a packet is received by dom0, then bridged into dom1, how is the
> system load proportioned between domains for the actual transfer of data
> between the two domains?
> 
> I guess what I'm asking is, is there a way to report the amount of cpu
> time is spent in xen itself and the corresponding system load? It would
> be nice to be able to see the load on the physical server as a whole for
> monitoring purposes, or is it sufficient to simply sum up the load on
> all the domains?

Very little time will be spent in Xen, as all the hard work is done
within guest context. However, the load reported by domains is
currently incorrect when they are preempted --- the domain will think
that whatever was running at the time it got preempted ran for the
entire time that in fact someone else was running. :-(

We have some ideas for how to fix this, but in fact what you really
need is for Xen to record load stats on each CPU (who ran for how much
on each one) and report that to control software. That also shouldn't
be too hard to add.

 -- Keir


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