Messages in this thread | | | Date | Thu, 7 Jul 2016 13:09:21 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 0/4] implement vcpu preempted check |
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On Thu, Jul 07, 2016 at 11:42:15AM +0200, Peter Zijlstra wrote: > I suspect you want something like so; except this has holes in. > > We clear KVM_ST_PAD_PREEMPT before disabling preemption and we set it > after enabling it, this means that if we get preempted in between, the > vcpu is reported as running even though it very much is not. > > Fixing that requires much larger surgery.
Note that this same hole is already a 'problem' for steal time accounting. The thread can accrue further delays (iow steal time) after we've called record_steal_time(). These delays will go unaccounted.
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