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This adds code to measure "stolen" time per virtual core in units of timebase ticks, and to report the stolen time to the guest using the dispatch trace log (DTL). The guest can register an area of memory for the DTL for a given vcpu. The DTL is a ring buffer where KVM fills in one entry every time it enters the guest for that vcpu. Stolen time is measured as time when the virtual core is not running, either because the vcore is not runnable (e.g. some of its vcpus are executing elsewhere in the kernel or in userspace), or when the vcpu thread that is running the vcore is preempted. This includes time when all the vcpus are idle (i.e. have executed the H_CEDE hypercall), which is OK because the guest accounts stolen time while idle as idle time. Each vcpu keeps a record of how much stolen time has been reported to the guest for that vcpu so far. When we are about to enter the guest, we create a new DTL entry (if the guest vcpu has a DTL) and report the difference between total stolen time for the vcore and stolen time reported so far for the vcpu as the "enqueue to dispatch" time in the DTL entry. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de> Signed-off-by: Avi Kivity <avi@redhat.com> |
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