Betriebssysteme · Institut für Systemarchitektur · Fakultät Informatik · TU Dresden



19. 10. 2017

Measuring the Effects of Turbo on VMs


Ben Serebrin

Google

Sondertermin: 16:30 Uhr, APB 3105

Turbo modes allow CPUs to operate above their specified base frequency. Modern CPUs change frequency dynamically and often due to CPU load, power consumption, temperature, cooling capacity of the system, and CPU SKU. A socket with half of its CPUs idle may run its active CPUs at a higher frequency than a socket with all CPUs busy.
VMs expect consistent performance, which is in tension with turbo in a datacenter. A lightly-loaded host may provide better VM performance than a heavily-loaded host, and hosts have varying levels of load that are not directly visible to the VMs. Datacenter forensics on performance variation is valuable, but turbo effects were invisible to our performance monitoring trackers.
This talk discusses upstream patches that track a VM's per-VCPU turbo history. We describe turbo observations and measuring turbo occupancy per VM in our datacenters.
10. Dec 2018
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