Bankers Algorithm
- Motivation: Avoid deadlocks when working with threads
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Idea: When a thread requests a resource, the OS checks if it would deadlock
- If so, wait for other threads to release resources
- If not, grant the resource right away
- Implementation: State max resources that thread needs. Allow thread to proceed if
available resources - requested resources >= max remaining needed by any thread - Keeps system in a safe state
Precise Exceptions
At the time that an exception handler begins execution, there is a well-defined instruction address in the instruction stream for which all prior instructions have committed their results and no following instructions (including the excepting one) have modified processor state.
Meltdown Security Flaw
Many processors allowed timing windows in which illegal accesses could be performed speculatively and made to impact cache state – even though the speculatively loaded data was later squashed in the pipeline and could not be directly used.
Earliest Deadline First(EDF) scheduler
- The scheduler to use for realtime systems. Runs the task with the earliest deadline first.
Beladys anomaly
- Increasing number of page frames increases number of page faults for FIFO, Random Page Replacement