CPU Scheduling and Memory Management in Distributed Systems

Many high-performance distributed systems encounter bottlenecks not within their application code, but at the operating system (OS) level.

A system with abundant hardware can still suffer from high latency and low throughput, often because of the fundamental decisions the OS makes every millisecond about how to allocate CPU time and manage memory. Understanding these core mechanics is critical for designing scalable and reliable systems.

This lesson examines how the OS’s CPU scheduler and memory manager operate and why their behavior is essential for building predictable, high-performance applications.

Overview of CPU scheduling and memory management

Every application running on a computer, from a web server to a database, competes for two primary resources: CPU cycles and memory. The OS acts as a traffic controller, managing access to these resources to ensure fairness and efficiency.

This management process is divided into two key areas:

• CPU scheduling: It determines which ready-to-run process gets to use the CPU and for how long.

• Memory management: It controls how memory is allocated to processes, keeping them isolated from one another and providing abstractions like virtual memoryA memory management technique that extends a computer's physical RAM (Random Access Memory) by using a portion of the hard drive or solid-state drive (SSD) as "virtual" RAM..

The diagram below illustrates this core relationship, showing how the OS kernelThe central part of an operating system that acts as a bridge between the software and hardware of a computer. mediates between applications and hardware.

In a distributed system, these low-level decisions have magnified consequences.

Inefficient scheduling on one node can create a bottleneck that slows down the entire system, while poor memory management can lead to crashes or latency spikes that violate SLOsService level objectives is a specific, measurable, and agreed-upon target for the performance or reliability of a service.. The first step in understanding how the OS manages CPU allocation and prevents performance issues is to explore how the scheduler determines which process will receive the CPU next.

Preemptive CPU scheduling

CPU scheduling determines the order in which processes are executed.

To understand this, imagine a debate: in a non-preemptive Non-preemptive scheduling requires a process to run to completion or until it voluntarily yields the CPU. model, a ...