OS Week 2

• CPU is one of the most important resources in a computer.
• Scheduling/policy in CPU decides which code to run next.
• The mechanism in CPU is Context Swap.
• Execution context in CPU is a set of information that needs to be preserved to maintain the illusion that a piece of code is always running on the CPU.
• General registers in CPU range from 8 to 128, depending on the architecture.
• In Context Swap, the running context from the CPU is saved into memory.
• SP (Stack Pointer) is a register in the CPU.
• IP (Instruction Pointer) is a register in the CPU.
• Config register is a register in the CPU.
• Context Swap is the process of switching between contexts.
• SR (Status register) is a register in the CPU.
• Everything else on main mem, stack, etc. is not a register in the CPU.
• The scheduler then picks the next context.
• GP (General Purpose) is a register in the CPU.
• Process: Massive container used to account for all kinds of resources, with one execution context and kernel swaps between processes.
• Thread: Single execution context and stack within a process, with the process able to have more than one thread.
• Kernel-level thread: Managed, scheduled, and swapped by the kernel.
• User-level thread: Opaque to the kernel and managed by code running within the process itself.
• Process switching is slow.
• Threads in the same address space can communicate directly with memory.
• Threads in the same address space can use special synchronization primitives provided by the architecture.