Notes / GATE / Operating Systems

CH 01

Scheduling, deadlock, paging

Operating Systems · GATE

Key points

  • SJF gives the minimum average waiting time (among non-preemptive); SRTF is its preemptive version.
  • 4 conditions for deadlock: mutual exclusion, hold & wait, no preemption, circular wait.
  • Banker's algorithm is for deadlock avoidance.
  • Belady's anomaly occurs in FIFO, not in LRU or Optimal.
  • Deadlock-free condition: n processes, each needing max k resources → resources ≥ n(k − 1) + 1.

Formulas & facts

Turnaround time
Completion − Arrival
Waiting time
Turnaround − Burst
EMAT (TLB)
h(t + m) + (1 − h)(t + 2m)
Page table size
Entries × entry size
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