Questions and Answers
¿Qué limita la multiprogramación en particiones de tamaño fijo?
La cantidad de particiones disponibles
¿Por qué las particiones de tamaño fijo desperdician memoria?
Porque no se ajustan al tamaño de los procesos
¿Cuál es una mejora de las particiones de tamaño variable sobre las de tamaño fijo?
Aprovechan mejor la memoria disponible
¿Qué mantiene el sistema operativo en una tabla?
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¿Qué sucede con toda la memoria de usuario al inicio del sistema?
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¿Qué debe hacer el sistema operativo cuando un nuevo proceso comienza?
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¿Qué puede tener que hacer el sistema operativo para acomodar un proceso en un agujero existente?
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¿Qué sucede con el área de memoria de un proceso cuando este termina?
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¿Qué es la fragmentación?
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¿Qué es la compactación?
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Study Notes
- Fixed-size partitions limit multiprogramming to the number of available partitions
- Fixed-size partitions waste memory
- Variable-size partitions are an improvement over fixed-size partitions
- The operating system maintains a table of occupied memory areas
- At system startup, all user memory is free and constitutes a large hole
- When a new process starts, the OS must find a hole large enough to accommodate it
- The OS may have to split a larger hole into smaller ones to accommodate a process
- When a process ends, its memory area becomes a hole that can be used for future processes
- Fragmentation can occur when there are too many small holes that cannot be used for larger processes
- Compaction can be used to reduce fragmentation by moving processes and consolidating holes.
- Memory allocation is a process where a process is loaded into memory and competes for CPU resources.
- New processes waiting for memory allocation are managed by the operating system with a memory allocation algorithm.
- When a process is loaded into memory, a hole large enough to accommodate it is searched for.
- If the hole is larger than the process, it is divided into two parts, one assigned to the process and the other creating a smaller leftover hole.
- When a process leaves memory, the space it frees up creates a new hole, which can be merged with adjacent holes.
- Three strategies for allocating holes to processes are: first fit, best fit, and worst fit.
- First fit simply assigns the first available hole that is large enough.
- Best fit searches for the smallest available hole that is large enough, creating smaller leftover holes.
- Worst fit searches for the largest available hole that is capable of accommodating the process, creating larger leftover holes.
- In general, first fit and best fit are more efficient than worst fit.
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