Patch: cpu utilization monitor.

[linas at austin.ibm.com]

On Wed, Mar 17, 2004 at 11:13:59AM -0800, Dave Hansen wrote:
> On Wed, 2004-03-17 at 10:56, linas at austin.ibm.com wrote:
> > This patch differs from other efforts in that it gets data directly from
> > the hypervisor.  Think multiple virtual cpus running on one physical cpu.
> > The traditional tools, whether CKRM or top or vmstat, are blind to the
> > fact that any given 'virtual cpu' might be getting only 10% of the physical
> > cycles in one hypervisor time-slice, and 90% in another.
> >
> > Very crudely, its sort-of like VM on the 390/zSeries.  Your kernel may
> > think its 100% busy, but in fact it might be getting only 1% of the actual
> > physical hardware cycles.  The goal here is to be able to report the
> > fraction of the total physical cycles, and do so on a HZ or even sub-HZ
> > level of granularity.
>
> But, the number is still just another performance counter, right?  Is

Yes.

> the interface to fetch it the same as the other CPU performance
> counters?

Maybe.  I don't know where/how top, vmstat, ckrm get thier data.
I don't know if the top/vmstat/ckrm authors are even interested
in having this data.

The current patch merely gathers the data in a 'correct' fashion;
there are some users for it, but the last word has not yet been written
as to how to present the data.  I think Manish is open to suggestion.
I for one, don't know how to 'give' the data to ckrm, but maybe that
will become clear in a later thread?

Yes, eWLM is one of the users; the local performance team is interested
too.

--linas

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