On the feasibility of memory sharing: Content-based page sharing in the xen virtual machine monitor

This thesis evaluates the feasibility of doing page sharing between virtual machines. To do this evaluation we proposed two different de-signs: One that is transparent to the guest op-erating system and a paravirtualized one. We implemented one of these based on Potemkin, which is a modification of the Xen virtual ma-chine monitor. In this we find pages eligi-ble for sharing by use of a technique called content-based page sharing. When identical pages are found, the actual sharing of pages is obtained using shadow page tables and Copy-on-Write. Finally the implementation was evaluated and we found no significant over-heads except for the use of shadow page ta-bles. The paravirtualized design should miti-gate this overhead. As for the feasibility of page sharing, we car-ried out a series of experiments. These ex-plored sharing under good and bad conditions as well as under synthetic workloads. We con-cluded that page sharing is feasible and that most workloads that have similar kernels and applications have something to share