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CSC 711 Cheat Sheet

Memory management

• i386: 10-10-12 two-level paging; CR3 -> PDE -> PTE; 4 KB pages.
• PTE 32 bits: frame in 31-12; flags P,R/W,U/S,PWT,PCD,A,D,PAT,G + AVL.
• 4 KB pages, 32-bit: offset 12, page number 20, 2^20=1,048,576 PTEs, 4 MB per process flat.
• MMU: walks tables, checks P/U-S/R-W, sets A and D, caches in TLB.

File systems

• FAT: linked allocation (follow chain); System V: indexed inode (10 direct + indirect); FFS: indexed + locality.
• FFS wins (C-B-F-B): Cylinder groups, Big blocks, Fragments, Bitmaps.
• Locality of reference -> short seeks -> large throughput gain over System V.

I/O, structure, deadlock

• I/O layers: hardware -> interrupt handler -> device driver -> device-independent -> user-level.
• DMA: one interrupt per block (not per byte); CPU freed.
• Monolithic = speed; microkernel = reliability + extensibility (pays IPC tax).
• Coffman M-H-N-C: Mutual exclusion, Hold-and-wait, No preemption, Circular wait.
• Prevention (rules), Avoidance (Banker's/safe state), Detection (wait-for cycle + recovery).

Scheduling

• States: Ready / Running / Blocked; Running->Ready = pre-emption.
• FCFS batch (convoy effect); RR interactive (quantum-sensitive); Timeslice Priority (importance); MLFQ general mixed.
• Keywords: aging, priority inversion, quantum, convoy effect.

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