vault backup: 2022-10-30 22:03:04

content/notes/21-memory-management.md

@@ -11,8 +11,24 @@ tags:
 primary storage - cache and main memory
 secondaryy - hard drive
 
-# process memory image
+as we move from secondary to primary:
+- access speed increases
+- access time decreases
+- cost increases
+- capacity decreases
+
+# process memory image and logical and physical addresses
+ - a program is compiled and linked into a process image before loading into memory for execution 
+ - a process memory image consists of code section, data sections, lib sections, and stack sections 
+ - each process has its own logical memory space starting from 0 and ending at a maximum address 
+ - the logical address has to be translated into physical address before sending the memory request to the physical memory modules 
+ - the memory management unit (MMU) translated between the logical addresse and the physical addresses. 
+ 
+ - physical mode - progam refers directly to physical address
+ - protected mode - dont allow program to use physical address directly - uses logical address
+ - OS kernel creates a map from logical address to the physical address using a mapping table
+ - CPUrefers to this table to map between physical and logical address
+
 
-# lgical and physical addresses
 
 # paging for memory translation