ACDC: Advanced consolidation for dynamic containers

The thriving success of the Cloud Industry greatly relies on the fact that virtual resources are as good as bare metal resources when it comes to ensuring a given level of quality of service. Thanks to the isolation provided by virtualisation techniques based on hypervisors, a big physical resource can be spatially multiplexed into smaller virtual resources which are easier to sell. Unfortunately, virtual machines have quickly shown their limit in terms of temporal multiplexing. It has been demonstrated that reclaiming the unused memory of a VM is a tedious task, infeasible in production. Today, containerization opens up a wide range of multiplexing opportunities that were not accessible through machine virtualization. However, in this article, we demonstrate, through a reproducible experiment, that the current implementation of memory consolidation can deteriorate the performance of applications deployed in Linux kernel containers. Indeed, we observed that when a new container boots, the memory of active containers is reclaimed while unused memory is still available in other containers that are inactive. To tackle these performance drop in active containers, we have rethought the hierarchical memory reclaim mechanism of the Linux kernel. We have implemented inside the kernel our new approach that tracks the container that has made a memory demand the least recently. Our evaluations show that our approach provides the ability to reclaim memory without disturbing performances.