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

On 21 Feb 2006, at 19:32, Rik van Riel wrote:

Basically steal time is the amount of time when:
1) we had a runnable task, but
2) it was not running, because our vcpu was scheduled
   away by the hypervisor

Thus, steal time measures how much a particular workload
inside a virtual machine is impacted by contention on the
cpu between different virtual machines.

It also makes sure that time the vcpu itself was not running
is not erroneously accounted to the currently running process,
which matters when a user is trying to determine how much CPU
time a particular task needs.

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?

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. :-)

 -- Keir

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