Reference Pattern-Aware Instant Memory Balancing for Consolidated Virtual Machineson Manycores

Memory contention among consolidated VMs on the same hardware has created the need for repetitive memory balancing operations. In an attempt to provide a prompt memory balancing mechanism, we found problems with the retardation of memory reallocation by the reclamation delay. The scheduling of the VMs and their VCPUs generates the delay, the dirtiness of the candidate pages for balancing makes the delay fluctuated, and a conflict of two reclamation policies between the guest OS and the hypervisor deteriorates the application performance. As a remedy to these problems, we propose HyperDealer2 (HD2), which selects the victim pages based on the reference patterns of clean pages, reclaims them with hypervisor-level paging, and reallocates those pages with explicit ballooning of the recipient guest OS. HD2 eliminates the involvement of victim VMs in memory reclamation and extends the dwell time of reclaimed pages in the reclaimed state. Consequently, HD2 significantly reduces the time taken to reallocate memory with a low overhead and enhances the value of additional memory for the recipient VMs. The experimental results of HD2 show that the execution time of memory-intensive applications in the recipient VM is reduced by up to 50 percent in spite of less than 2 percent performance penalty.