分片与压实的区别

在操作系统中，内存管理在最大化 CPU 利用率方面起着至关重要的作用，当空间分配给进程时，内存的一些损失（碎片）会导致内存的低效使用，而减少这种损失的技术之一（压缩) 用于优化内存空间。

碎片化

它是由于传染性内存分配而发生的，因为存在存储空间未达到最大值的现象。从而降低操作系统的性能。碎片有两种类型：外部碎片和内部碎片。

1. 外部：可用空间不连续，存储空间被划分为少量空洞时发生。 First fit 和 Best fit 都受到外部碎片的影响。

Example problem: Size of different non contagious small holes are 54 byte, 30 byte and 44 byte. Total non contagious size is- 54+30+44=128 bytes. Process request is 120 bytes.

Solution: Could not proceed due to non contiguous holes leads to external fragmentation.

内存中的外部碎片示例

2.内部：分配空间给进程后留在块中的内存导致内部碎片。分页存在内部碎片。内存内部碎片示例

Example problem: Available block size 255 bytes. Process size 250 bytes.

Solution:The process is allocated to the block, creating a hole of 5 bytes which leads to internal fragmentation.

内存内部碎片示例

压实

这是一种将孔（小内存块）向一个方向移动并将占用的块移动到另一侧的技术。大量的时间浪费在执行压缩上。

压实技术

分片和压实的区别

S. No	Fragmentation	Compaction
1.	It is due to the creation of holes (small chunks of memory space).	It is to manage the hole.
2.	This creates a loss of memory.	This reduces the loss of memory.
3.	Sometimes, the process cannot be accommodated.	Memory is optimized to accommodate the process.
4.	External Fragmentation may cause major problems.	It solves the issue of External Fragmentation.
5.	It depends on the amount of memory storage and the average process size.	It depends on the number of blocks occupied and the number of holes left.
6.	It occurs in contiguous and non-contiguous allocation.	It works only if the relocation is dynamic.