Developers working in a Linux environment should be aware of how the kernel manages memory and process scheduling. This guide provides an overview of memory management in Linux, with a focus on how it relates to IT development.
The Linux kernel is responsible for managing memory and process scheduling. It uses a variety of techniques to optimize memory usage and performance.
One of the most important aspects of memory management is the page cache. The page cache is a pool of free memory that is used to cache data from disk. When a process needs to read data from disk, the kernel first checks the page cache to see if the data is already in memory. If so, the data is read from memory instead of disk, which is much faster.
The page cache is important for performance, but it can also cause problems. If a process needs to read a large amount of data from disk, the page cache can quickly fill up. This can cause the system to run out of memory and start swapping, which is very slow.
To avoid this problem, the kernel uses a technique called "swappiness." Swappiness is a tunable parameter that controls how aggressively the kernel will use the page cache. A value of 0 means that the kernel will never swap, even if it means that the system will run out of memory. A value of 100 means that the kernel will always swap, even if it's not necessary.
The default value for swappiness is 60. This means that the kernel will use the page cache aggressively, but will still start swapping when necessary.
In addition to managing memory, the Linux kernel is also responsible for process scheduling. Processes are scheduled using a variety of algorithms, including the deadline scheduler, the fair scheduler, and the completely fair scheduler.
The deadline scheduler is designed for real-time processes that need to complete their work within a specific time period.
The fair scheduler is designed for batch processes that can run for a long time without interruption.
The completely fair scheduler is the default scheduler in most Linux distributions. It is designed to provide fair access to the CPU for all processes.
Memory management and process scheduling are important aspects of Linux development. Developers should be aware of how the kernel manages memory and process scheduling in order to optimize performance and avoid problems.