1.6 KiB
1.6 KiB
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