Conversion process from logical address to physical address

The CPU needs to take two steps to convert the addresses in a virtual memory space to physical addresses: first, we need to give a logical address (in fact, it is a segment offset. This must be understood !!!), The CPU needs to use its segmented Memory Management Unit to convert a logical address into a thread address, and then use its webpage Memory Management Unit to convert it to the final physical address.

Physical address)
UsedMemoryChip-level unit addressing corresponds to the address bus connected to the processor and CPU.
-- This concept should be better understood among these concepts, but it is worth mentioning that although physical addresses can be directly understood as the memory itself inserted on the machine, consider the memory as a large array of serial numbers from 0 bytes to the maximum number of NULL bytes, and then call this array a physical address. But in fact, this is only a hardware providedSoftwareMemory addressing is not like this. Therefore, it is more appropriate to say that it is "corresponding to the address bus", but aside from considerations of the physical memory addressing method, it directly maps the physical address to the physical memory one by one, it is also acceptable. Maybe wrong understanding is more conducive to the metaphysical image extraction.

 

Virtual Memory)
This is the image description of the entire memory (do not insert the upper number with the machine. It is relative to the physical memory, and can be directly understood as "not straight", "fake" memory, for example, a 0x08000000 memory address, it is not the address element of 0x08000000-1 in the large array on the physical address;
This is because the modern operating system provides a kind of memory management image, namely virtual memory ). The process uses the address in the virtual memory, and the operating system assists the relevant hardware to "convert" it into a real physical address. This "conversion" is the key to all discussions.
With this image,ProgramYou can use an address space that is much larger than the actual physical address. (The east wall, the west wall, and the bank do the same), and even multiple processes can use the same address. It's not surprising because the converted physical addresses are not the same.
-- You can decompile the connected program and check that the connector has allocated an address to the program. For example, to call a function,CodeInstead of call a, call 0x0811111111. That is to say, the address of function a has been fixed. Without such a "Conversion", there is no virtual address concept, and this is simply not feasible.

Logical Address)
Intel retains the segmented memory management methods of the ancient times for compatibility purposes. A logical address refers to the address in a machine language instruction that is used to specify an operand or an instruction. In the above example, the address 0x08111111 allocated by the connector for a is the logical address.
-Sorry, it seems that it violates Intel's middle-stage management requirements for logical addresses, "a logical address, it is expressed as [segment identifier: Intra-segment offset] by adding an offset of the relative address in the specified segment to a segment identifier, that is, the 0x08111111 in the preceding example, it should be represented as [A code segment identifier: 0x08111111], so that it is complete"

Linear address or virtual address)
Similar to the logical address, it is also an invalid address. If the logical address is the address before the segment Management Switch on the hardware platform, the linear address corresponds to the address before the hardware page memory conversion.

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