Section 8.7. Virtual Memory as a File System Cache

8.7. Virtual Memory as a File System Cache

The Solaris VM system implements many more functions than just management of application memory. In fact, the Solaris virtual memory system is responsible for managing most objects related to I/O and memory, including the kernel, user applications, shared libraries, and file systems. This strategy differs significantly from other operating systems like earlier versions of System V UNIX, where file system I/O used a separate disk cache.

One of the major advantages of using the VM system to manage file system caching is that all free memory in the system is available as a cache, providing significant performance improvements for applications that use the file system and removing the need for manual tuning of the size of the cache. The VM system can allocate all free memory for file system cache, meaning that on a typical system with file system I/O, almost all of the physical memory will be advantageously used.

In summary, the Solaris VM system performs these major functions:

• It manages virtual-to-physical mapping of memory.

• It manages the swapping of memory between primary and secondary storage to optimize performance.

• It handles requirements of shared images between multiple users and processes.

• It acts as an integrated file cache.