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Ricardo A. Baratto COMS E6118 – Spring 2004. Surplus Fair Scheduling. Proportional-Share CPU Scheduling for Symmetric Multiprocessors. What? Why?. Fair resource allocation Proportional to application's share WFQ [Demers et al.], [Parekh et al.], Stride [Waldspurger et al.]
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Ricardo A. Baratto COMS E6118 – Spring 2004 Surplus Fair Scheduling
Proportional-Share CPU Scheduling for Symmetric Multiprocessors
What? Why? • Fair resource allocation • Proportional to application's share • WFQ [Demers et al.], [Parekh et al.], Stride [Waldspurger et al.] • SFQ [Goyal et al.] • SMART [Nieh et al.]
The Problem • Unfeasible Weight Assignment: Starvation • Upper Bound on Assignment • Frequent Arrival – Departures: Unfairness • Burst Behavior
Surplus Fair Scheduling • Weight Readjustment • Generalized Multiprocessor Sharing(Surplus Approximation)
Weight Readjustment • Readjust threads violating feasibility constraint: • Optimal: • Number of threads • Weight change • Efficient • O(p)
GMS and Surplus Approximation • Generalization of GPS [Parekh et al.] • φi: Readjusted weight • Ai(t1, t2): CPU service received • Si: Weighted CPU service = Si + q/φi • αi = Ai(0, t) - AiGMS(0, t)≈ (φi . Si) - (φi . v)
SFS Algorithm • update Fi and compute Si • compute v: min(Si) • compute αi • schedule ti with min(αi) • If {t} changes: readjust weights
Implementation and Complexity • Three ordered queues: • w: Weight readjustment • S: Virtual time • α: Next to schedule • Add thread: Insert + Readjust = O(t+p) • Delete thread: Delete + Readjust = O(p) • Schedule: Update surplus + Sort = O(t log t) [~ every p schedules]
