CHiP: A Profiler to Measure the Effect of Cache Contention on Scalability

Brett, Bevin; Kumar, Pranith; Kim, Minjang; Kim, Hyesoon

doi:10.1109/ipdpsw.2013.49

Cited by 6 publications

(3 citation statements)

References 14 publications

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“…Throttling concurrency to improve throughput was also suggested by Raman et al [68] and Pusukuri et al [65]. Chandra et al [13] and Brett et al [6] analyzed the impact of inter-thread cache contention. Heirman et al [43] suggested intentional undersubscription of threads as a response to competition for shared caches.…”

Section: Related Workmentioning

confidence: 96%

“…* amenable to; subject to * Let thruput(n) be the thruput function for n threads thruput(n) vs n*thruput (1) • Socket-level resources LLC residency and DRAM channel bandwidth 5 Lock implementations themselves are sometimes a causative factor for collapse, for instance via induced coherence traffic on lock metadata or where lock algorithmic overheads increase with the number of contending or participating threads. 6 Contended locks just happen to be a convenient and opportunistic vehicle with which to restrict concurrency. Competition for core-level resources such as pipelines typically starts to manifest when the number of ready threads exceeds the number of cores, and more than one thread is running on a core.…”

Section: Taxonomy Of Shared Resourcesmentioning

confidence: 99%

“…• Socket-level resources LLC residency and DRAM channel bandwidth 5 Lock implementations themselves are sometimes a causative factor for collapse, for instance via induced coherence traffic on lock metadata or where lock algorithmic overheads increase with the number of contending or participating threads. 6 Contended locks just happen to be a convenient and opportunistic vehicle with which to restrict concurrency.…”

Section: Taxonomy Of Shared Resourcesmentioning

confidence: 99%

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Malthusian Locks

Dice

2017

Proceedings of the Twelfth European Conference on Computer Systems

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Applications running in modern multithreaded environments are sometimes overthreaded. The excess threads do not improve performance, and in fact may act to degrade performance via scalability collapse 1 , which can manifest even when there are fewer ready threads than available cores. Often, such software also has highly contended locks. We leveropportunistically Possible counter-argument or counter-example -example of applications that might suffer from unfair CR admission. Imagine a "ragged barrier" which does not satisfy rendezvous conditions until all participating threads have completed 10 loop steps. Each step acquires and releases a contended CR-based lock within the loop. The time to reach rendezvous may be longer with a CR-based locks than with strict FIFO locks. Drafty DraftWe draw an analogy-metaphor between threads and members of the populace. We anthropomorphize threads.arrived thread * Require saturation and contention and waiting threads for a lock to be able to decide which threads will be admitted. Require surplus. * sideline; passivate; arrest; detain; sequester; deactivate; suspend; capture; * Lock lore; folk myth; received wisdom; practicum; praxis; * CR = MCSCRA8U; LIFOE3; FOXD family; FIFO = TKT; CLH; MCS; * LOITER = FOXD family MCSCR = MCSCRA8U LIFOCR = LIFOE3 * CR : mostly-LIFO admission order * STP = Spin-then-park waiting policy Candidates for the name of lock algorithm and the paper title. * Venturi Effect : restrict flow implies reduce pressure and faster flow velocity; * Performance diode -only improves; never degrades; * http://www.newyorker.com/magazine/2011/02/07/crush-point * MPL = Multiprogramming level; * Tragedy of the commons = rational maximizing behaviors by individuals results in unsustainable overexploitation of a resource. * Performance is subadditive * Slower-is-Faster phenomenon * Concurrency control overheads are ultimately proportional to contention instead of actual throughput. * MTTR = Median-time-to-reacquire * TTR is always >= waiting time, measured in acquisitions. * Myriad ways exist to measure short-and long-term fairness. * Under an ideally fair FIFO lock, admission order corresponds perfectly with arrival order. * Define unfairness as : how admission order deviates from FIFO or how admission order deviates from arrival order. * LWSS Window size W should be larger than maximum number of concurrent participating threads.CR acts to reduce the number of distinct threads circulating through the lock over short intervals and thus tends to reduce the LWSS, while still providing long-term fairness. The CR admission policy must also be work conserving and never under-provision the lock. It should never be the case that the critical section remains intentionally unoccupied if there are waiting or arriving threads that might enter -if such threads exist, then one will promptly be enabled to do so.If arriving or waiting threads might enter the critical section, then one will be promptly enabled to do so. * The admission policy for an optimal CR implementation attempts to...

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