Recent Trends in Parallel Computing Review Article
Memory Reclamation Behavior Under cgroups v2 Versus Legacy cgroups: A Measurement Framework for Containerized Workloads
Abstract
Linux control groups (cgroups) are the kernel mechanism that lets container runtimes such as Docker, containerd, and CRI-O enforce per-container CPU, memory, and I/O limits, and the transition from the legacy cgroups v1 hierarchy to the unified cgroups v2 hierarchy changed several aspects of how the memory controller signals and responds to reclaim pressure most notably through the introduction of memory.low/memory.high soft-limit semantics and system-wide Pressure Stall Information (PSI). Kernel documentation and a small number of practitioner benchmarks describe these interface-level changes, and separate networking-focused studies have measured cgroups v2's lower CPU-instruction overhead relative to v1, but we are not aware of published work that measures, under controlled and reproducible conditions, how the two hierarchies actually behave when several memory-constrained containers compete for host memory on the same node—the scenario that determines achievable container density in practice. This paper makes two contributions. First, it synthesizes the documented and practitioner-reported differences between the v1 and v2 memory controllers into a specific set of hypotheses about reclaim behavior under contention (soft-limit responsiveness, page-cache versus anonymous-memory eviction balance, and OOM-kill fairness across co-located containers). Second, it specifies a controlled, reproducible benchmark protocol using a memory-pressure workload generator, a fixed host configuration, and a defined density-scaling procedure for testing these hypotheses directly, and it reports the results section as an execution plan with the intended tables rather than fabricated benchmark numbers, since the benchmark has not yet been run on physical or virtualized hardware at the time of writing. The protocol is designed so that any reader with access to a Linux host supporting both hierarchies can execute it and populate the results independently.
Keywords
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