Scheduler-Conscious Synchronization.

Kontothanassis, Leonidas I.; Wiśniewski, Rafał; Scott, M. L.

doi:10.21236/ada290021

Cited by 8 publications

(7 citation statements)

References 16 publications

(28 reference statements)

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“…Imagine the code running on a two-processors machine: after main completes its execution, each philosopher embarks on a busy-waiting loop, only that two of them will be running in processors, while the third is (and will indefinitely remain) in the run-pool. Situations of deadlocks comprising suspended code are known to be difficult to deal with [13]. Our notion of deadlocked state takes into account running and suspended threads.…”

Section: Introductionmentioning

confidence: 99%

Type Inference for Deadlock Detection in a Multithreaded Polymorphic Typed Assembly Language

Vasconcelos

Martins

Cogumbreiro

2010

Electron. Proc. Theor. Comput. Sci.

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We previously developed a polymorphic type system and a type checker for a multithreaded lockbased polymorphic typed assembly language (MIL) that ensures that well-typed programs do not encounter race conditions. This paper extends such work by taking into consideration deadlocks. The extended type system verifies that locks are acquired in the proper order. Towards this end we require a language with annotations that specify the locking order. Rather than asking the programmer (or the compiler's backend) to specifically annotate each newly introduced lock, we present an algorithm to infer the annotations. The result is a type checker whose input language is non-decorated as before, but that further checks that programs are exempt from deadlocks.

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Section: Introductionmentioning

confidence: 99%

Type Inference for Deadlock Detection in a Multithreaded Polymorphic Typed Assembly Language

Vasconcelos

Martins

Cogumbreiro

2010

Electron. Proc. Theor. Comput. Sci.

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“…21 Competitive succession is also called barging, as arriving threads can barge in front of other waiting threads, allowing unbounded bypass and grossly unfair admission. 22 Kontothanassis et al [50] and He et al [42] suggested ways to mitigate this problem for MCS locks. 23 Unpark itself incurs a cost of more than 9000 cycles to the caller on our SPARC T5 system.…”

Section: Reentrantlockmentioning

confidence: 99%

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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“…Preemption, blocking, page faulting, and many other hazards that can befall the lock holder can be addressed through the use of scheduler-conscious synchronization [8]. Some form of scheduler-conscious synchronization is supported by each of the mainstream operating systems, including Linux, due to the fact that it is relied on by certain database kernels.…”

Section: Improving Lockingmentioning

confidence: 99%

Why the grass may not be greener on the other side

McKenney

Michael

Walpole

2007

Proceedings of the 4th Workshop on Programming Languages and Operating Systems

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The advent of multi-core and multi-threaded processor architectures highlights the need to address the well-known shortcomings of the ubiquitous lock-based synchronization mechanisms. The emerging transactional-memory synchronization mechanism is viewed as a promising alternative to locking for high-concurrency environments, including operating systems. This paper presents a constructive critique of locking and transactional memory: their strengths, weaknesses, and challenges.

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Scheduler-Conscious Synchronization.

Cited by 8 publications

References 16 publications

Type Inference for Deadlock Detection in a Multithreaded Polymorphic Typed Assembly Language

Type Inference for Deadlock Detection in a Multithreaded Polymorphic Typed Assembly Language

Malthusian Locks

Why the grass may not be greener on the other side

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