Squeezy: Rapid VM Memory Reclamation for Serverless Functions

TL;DR

Squeezy is a novel Linux-based approach that enables rapid and efficient VM memory hot-unplug for serverless functions, significantly reducing reclamation latency and improving resource elasticity in FaaS environments.

Contribution

The paper introduces Squeezy, a new method for fast VM memory hot-unplug by segregating memory regions, implemented as a Linux extension, improving reclamation speed for serverless computing.

Findings

Squeezy achieves sub-second reclamation of multiple GiBs of memory.

It is an order-of-magnitude faster than existing methods.

Maintains bounded tail latency during memory reclamation.

Abstract

Resource elasticity is one of the key defining characteristics of the Function-as-a-Service (FaaS) serverless computing paradigm. While compute resources assigned to VM-sandboxed functions can be seamlessly adjusted on the fly, memory elasticity remains challenging. Hot(un)plugging memory resources suffers from long reclamation latencies and occupies valuable CPU resources. We identify the obliviousness of the OS memory manager to the hotplugged memory as the key issue hindering hot-unplug performance, and design Squeezy, a novel approach for fast and efficient VM memory hot(un)plug, targeting VM-sandboxed serverless functions. Our key insight is that by segregating hotplugged memory regions from regular VM memory, we are able to bound the lifetime of allocations within these regions thus enabling their fast and efficient reclamation. We implement Squeezy in Linux v6.6 as an extension to the OS memory manager. Our evaluation reveals that Squeezy is an order-of-magnitude faster than state-of-the-art, keeping tail latency bounded, when reclaiming VM memory, achieving sub-second reclamation of multiple GiBs of memory while serving realistic FaaS load.