2024-01-22 10:12:47

UNB/Year 4/Semester 1/CS3418/9-20-2023.md

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+Lecture Topic: Processes
+Parts of memory
+- Stack
+- Heap
+- Program Counter
+- Registers
+- Arguments Vector
+- Environment PATH
+
+| Stack Layout                   |
+| ------------------------------ |
+| argv, argc                     |
+| stack                          |
+| heap                           |
+| uninitialized global variables |
+| initialized global variables   |
+| text                               |
+
+Heap Memory, only the result of calls to malloc or calloc
+Stack Memory, anything else, even pointers or custom typedefs, unless it was specifically allocated
+
+Possible Process States
+- New: First Stage, when the OS loads the program and before it is given CPU cycles
+- Ready: When the program is ready to execute and has been added to the OS queue for execution
+- Running:  The program is executing instructions on the CPU
+- Waiting: The program is waiting for CPU cycles or is dormant, either due to timeout or waiting for IO or events
+- Terminated: The program memory is unallocated and revoked. Can be invoked by program itself or by parent (includes OS)
+
+Process Control Block or Task Control Block
+- Process state
+- Program counter
+- Scheduling information
+- Memory info
+- Accounting info
+- IO status info (fds, etc)
+In Linux this is implemented with a structure called `task_struct`
+
+It's organized in a Linked List, it's used for scheduling.
+
+The process scheduler, selects which process get CPU attention, with the goal of improving response time, as well as multiprorgramming.
+
+Maintained Queues
+- Waiting Queue
+- Ready Queue
+
+Processes could be CPU bound or IO bound
+
+In general 100% utilization (CPU, IO) is not bad