Oscillations: The Rhythmic Heartbeat of Physics Oscillations describe any system that moves back and forth in a periodic manner. The most familiar example might be the swinging of a pendulum, but oscillatory behavior occurs in countless natural systems, from the vibrations of molecules to the orbits of celestial bodies. Key Concepts in Oscillations: Simple Harmonic Motion (SHM) : This is the most basic type of oscillation, where the restoring force acting on an object is proportional to its displacement. Classic examples include a mass on a spring or a pendulum swinging with small amplitudes. The equations governing SHM are simple, but they form the basis for understanding more complex oscillatory systems. Damped and Driven Oscillations : In real-world systems, oscillations tend to lose energy over time due to friction or air resistance, leading to damped oscillations . In contrast, driven oscillations occur when an external force continuously adds energy to the system, preventing i
Swap-Space Management
* Modern systems typically swap out pages as required, other than swapping out entire processes. Hence the swapping system is bit of the virtual memory management system.
* Managing swap space is clearly an important task for modern OSes.
Swap-Space Use
* The amount of swap space required by an OS varies greatly according to how it is used. Some systems require an amount equal to physical RAM; some want a more of that; some want an amount same to the amount by which virtual memory exceeds physical RAM, and some systems use less or none at all!
* Some systems support more swap spaces on separate disks in order to speed up the virtual memory system.
Swap-Space Location
Swap space can be visibally located in one of two locations:
* As a large file which is part of the regular file system. This is easy to implement, but
inefficient. Not only must the swap space be processed through the directory system, the file is also subject to fragmentation issues. Caching the block location helps in detecting the physical blocks, but that is not a complete fix.
* As a raw partition, possibly on a single or little-used disk. This permits the OS more control over swap space management, which is usually faster and more efficient.
Fragmentation of swap space is generally not a big issue, as the space is retrieved every time the system is rebooted. The downside of placing swap space on a raw splitting is that it can only be grown by resplittening the hard drive.
Swap-Space Management: An Example
* Historically OSes swapped out entire processes as required. Modern systems swap out only individual pages, and only as required. (For example process code blocks and other blocks that have not been moved since they were originally loaded are normally just freed from the virtual memory system rather than copying them to swap space, because it is speeder to go detect them again in the file system and read them back in from there than to
write them out to swap space and then read them again.)
* In the mapping system shown below for Linux systems, a map of swap space is kept in memory, where each entry matches to a 4K block in the swap space. Zeros implies free slots and non-zeros refer to how many processes have a mapping to that particular block (>1 for shared pages only.)
