Section: New Results

Memory management for multicores

Participants : Antoine Blin, Damien Carver, Maxime Lorrillere, Sébastien Monnet, Julien Sopena [correspondent] .

Regal co-advises with Whisper team the PhD of Antoine Blin. The thesis focusses on modern complex embedded systems that involve a mix of real-time and best effort applications. The recent emergence of low-cost multicore processors raises the possibility of running both kinds of applications on a single machine, with virtualization ensuring isolation. Nevertheless, memory contention can introduce other sources of delay, that can lead to missed deadlines. We first investigated the source of memory contention for the Mibench benchmark in a paper published at ETYS 2016 [25]. Then, in a paper published at ECRTS 2016 [24], we present a combined offline/online memory bandwidth monitoring approach. Our approach estimates and limits the impact of the memory contention incurred by the best-effort applications on the execution time of the real-time application. Using our approach, the system designer can limit the overhead on the real-time application to under 5% of its expected execution time, while still enabling progress of the best-effort applications.

Another memory management challenge for multi-cores is the fragmentation induced by the virtualized environments. Previously, we proposed Puma (for Pooling Unused Memory in Virtual Machines) which allows I/O intensive applications running on top of VMs to benefit of large caches. This was realized by providing a remote caching mechanism that provides the ability for any VM to extend its cache using the memory of other VMs located either in the same or in a different host. This work was defended by Maxime Lorrillere in April 2016 [2].

More recently, we study the memory arbitration between containers. In the Damien Carver’s PhD thesis (started in October 2015), we are designing ACDC (Advanced Consolidation for Dynamic Containers), a kernel-level mechanisms that automatically provides more memory to the most active containers.