Amount of resource after n lotteries response time

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Unformatted text preview: holds t tickets, T total tickets • Probability of winning a lottery? • amount of resource after n lotteries? • response time inversely proportional to ticket allocation expected # of lotteries n that client must wait to win: Lottery Lottery Scheduling Advantages Proportional-share fairness • direct control over service rates Supports dynamic environments • immediately adapts to changes • fair chance to win each allocation No starvation • hold a non-zero # of tickets Flexible Flexible Resource Management Ticket transfers • explicit transfer between clients • when is this useful? Blocking, Blocking, prevent priority inversion Flexible Flexible Resource Management Compensation tickets • if don’t use full Q, your tickets are inflated in value … to ensure rate of consumption guaranteed by the share share Ticket Ticket Currencies Tickets denominated in currencies Modular resource management • locally contain effects of inflation • isolates loads across logical trust boundaries Currency Currency Implementation Kernel Kernel Implementation Objects: ticket, currency Operations • create/destroy ticket, currency • fund/unfund currency • compute value of ticket Relative Relative Rates Fairness Fairness Over Time Query Query Processing Rates Server has no tickets, clients transfer their tickets to it for a query Currencies Currencies Insulate Loads local inflation of B2 does not impact A Impressions? Impressions? BREAK BREAK Project Project #1 OS kernel TOP CPU I/O devices OS->CPU: run user program; run driver code CPU->OS: P instr (if exception), C, E, I syscalls Device->OS: I/O completes via interrupt/signal OS->Device: schedule future I/O Goal: OS to create, context-switch, terminate, run user processes and deal with the hardware Project Project #1 CPU: Mode bit PC: fetch instruction at this address, execute, …. VC: value register to be updated Project Project #1 Kernel: Maintain list of processes and their status Per process accounting I/O I/O device status Process “machine”state Scheduling: RR, Lottery scheduling Boot time: set up h/w run initial user program loop until no more processes to schedule Project Project #1 Process: Kernel state VAS: text segment local PC, local value (~ VC) local PC starts at 0 Project Project #1 S x : store x to VC A x : add x to VC D x : decr x from VC C <priority> <file-name> : create a process with the given <priority> priority using file-name (a code file) E : terminate the current process I <dev-class> (B/C) : IO syscall req...
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