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