utmem: Towards Memory Elasticity in Cloud Workloads

In environments where multiple virtual machines are colocated on the same physical host, the semantic gap between the host and the guests leads to suboptimal memory management. Solutions such as ballooning are unable to modify the amount of memory available to the guest fast enough to avoid performance degradation. Alternatives such as Transcendent Memory allow the guest to use host memory instead of swapping to disk. All these techniques are applied at the memory management subsystem level, resulting in cases where abrupt changes in memory utilization cause unnecessary guest-side swapping. We propose Userspace Transcendent Memory (utmem), a version of Transcendent Memory that can be directly utilized by applications without interference from the guest OS. Our results demonstrate that our approach succeeds in allowing the guests to rapidly adjust the amount of memory they use more efficiently than both ballooning and Transcendent Memory.