1. how you understand the operating system's memory fragmentation, what's the solution?
Inspection point: memory fragmentation
Reference answer:
Memory chips are divided into: internal fragmentation and external fragmentation.
Internal fragmentation that has already been allocated (you can pinpoint which part of the process) can not use the memory space;
Internal fragmentation or inner area of the page is in the internal memory block. Possession of these areas or pages of the process does not use this memory block. And in the process occupy this memory block, the system can not use it. When the process until it is released, or the end of the process, the system will it be possible to use this memory block.
Single channel allocated only continuous internal fragmentation. Fixed continuous multi-channel distribution both internal fragmentation, there are external fragmentation.
External fragmentation refers to has not been allocated (does not belong to any process), but too small can not be assigned to the new application process memory space of memory free area.
External debris out of any free memory blocks allocated region or outside of the page. The sum of these current memory block to meet the length requirements of the application, but because of their addresses are not continuous, or for other reasons, so that the system can not meet the current application.
Use the buddy system algorithm.
2. explain, what is paged memory?
Inspection point: Page Storage
Reference answer:
Main memory is equally divided into equal-sized pieces, called main memory block, also called a real page.
When a user program into memory, in units of pages allocated. Page size is 2n, usually 1KB, 2KB, 2n KB, etc.