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Re: [Xen-devel] [PATCH 1/2] cpu steal time accounting

On Wed, 22 Feb 2006, Keir Fraser wrote:

> Is accounting user/system time an unnecessary extra? I guess we already 
> do it by sampling at tick granularity anyway?
> Should 'steal time' include blocked time when the guest had no work to 
> execute?

No, this is idle time.  If the guest had no work to do,
it wasn't suffering from contention of the CPU.

> Also, given the logic currently only triggers when the guest detects it
> 'missed a tick', would it be good enough simply to account #missed_ticks as
> steal time. It would certainly be a lot simpler to implement, and you end up
> dividing everything down to tick granularity anyway. :-)

Not good enough if the hypervisor ends up scheduling
guests on a granularity finer than the guest's own
timer ticks.

The reason for only checking steal time when we miss
a tick is that I don't want to run the (expensive?)
steal time logic on every timer interrupt.

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