TLDR: A monolithic kernel is an operating system architecture where the entire kernel, including core system services like memory management, process scheduling, and device drivers, operates in a single kernel space. This design enables efficient communication between components, resulting in high performance. Monolithic kernels are widely used in systems like Linux, introduced by Linus Torvalds in 1991, and have proven reliable in diverse environments, from desktops to supercomputers.
https://en.wikipedia.org/wiki/Monolithic_kernel
In a monolithic kernel, all core functionalities and drivers are part of the same kernel image, allowing seamless interaction without the overhead of context switching, as seen in microkernel architectures. While this integration boosts performance, it also increases complexity. Errors in the kernel code can potentially impact the entire system, making rigorous testing and quality assurance critical for maintaining stability and reliability.
Modern monolithic kernels like the Linux Kernel mitigate potential downsides with features like dynamically loadable modules. This approach allows non-essential drivers and components to be added or removed at runtime without recompiling the kernel, enhancing flexibility. Despite alternatives like microkernels, the monolithic kernel remains a popular choice due to its balance of simplicity, performance, and extensive hardware support.