3 Search Results for "Jayanti, Prasad"


Document
Durable Algorithms for Writable LL/SC and CAS with Dynamic Joining

Authors: Prasad Jayanti, Siddhartha Jayanti, and Sucharita Jayanti

Published in: LIPIcs, Volume 281, 37th International Symposium on Distributed Computing (DISC 2023)


Abstract
We present durable implementations for two well known universal primitives - CAS (compare-and-swap), and its ABA-free counter-part LLSC (load-linked, store-conditional). Our implementations satisfy method-based recoverable linearizability (MRL) and method-based detectability (M-detectability) - novel correctness conditions that require only a simple usage pattern to guarantee resilience to individual process crashes (and system-wide crashes), including in implementations with nesting. Additionally, our implementations are: writable, meaning they support a Write() operation; have constant time complexity per operation; allow for dynamic joining, meaning newly created processes (a.k.a. threads) of arbitrary names can join a protocol and access our implementations; and have adaptive space complexity, meaning the space use scales in the number of processes n that actually use the objects, as opposed to previous protocols whose space complexity depends on N, the maximum number of processes that the protocol is designed for. Our durable Writable-CAS implementation, DuraCAS, requires O(m + n) space to support m objects that get accessed by n processes, improving on the state-of-the-art O(m + N²). By definition, LLSC objects must store "contexts" in addition to object values. Our Writable-LLSC implementation, DuraLL, requires O(m + n + C) space, where C is the number of "contexts" stored across all the objects. While LLSC has an advantage over CAS due to being ABA-free, the object definition seems to require additional space usage. To address this trade-off, we define an External Context (EC) variant of LLSC. Our EC Writable-LLSC implementation is ABA-free and has a space complexity of just O(m + n). To our knowledge, our algorithms are the first durable CAS algorithms that allow for dynamic joining, and are the first to exhibit adaptive space complexity. To our knowledge, we are the first to implement any type of durable LLSC objects.

Cite as

Prasad Jayanti, Siddhartha Jayanti, and Sucharita Jayanti. Durable Algorithms for Writable LL/SC and CAS with Dynamic Joining. In 37th International Symposium on Distributed Computing (DISC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 281, pp. 25:1-25:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{jayanti_et_al:LIPIcs.DISC.2023.25,
  author =	{Jayanti, Prasad and Jayanti, Siddhartha and Jayanti, Sucharita},
  title =	{{Durable Algorithms for Writable LL/SC and CAS with Dynamic Joining}},
  booktitle =	{37th International Symposium on Distributed Computing (DISC 2023)},
  pages =	{25:1--25:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-301-0},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{281},
  editor =	{Oshman, Rotem},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2023.25},
  URN =		{urn:nbn:de:0030-drops-191510},
  doi =		{10.4230/LIPIcs.DISC.2023.25},
  annote =	{Keywords: durable, recoverable, detectable, persistent memory, dynamic joining, LL/SC, CAS}
}
Document
Allocate-On-Use Space Complexity of Shared-Memory Algorithms

Authors: James Aspnes, Bernhard Haeupler, Alexander Tong, and Philipp Woelfel

Published in: LIPIcs, Volume 121, 32nd International Symposium on Distributed Computing (DISC 2018)


Abstract
Many fundamental problems in shared-memory distributed computing, including mutual exclusion [James E. Burns and Nancy A. Lynch, 1993], consensus [Leqi Zhu, 2016], and implementations of many sequential objects [Prasad Jayanti et al., 2000], are known to require linear space in the worst case. However, these lower bounds all work by constructing particular executions for any given algorithm that may be both very long and very improbable. The significance of these bounds is justified by an assumption that any space that is used in some execution must be allocated for all executions. This assumption is not consistent with the storage allocation mechanisms of actual practical systems. We consider the consequences of adopting a per-execution approach to space complexity, where an object only counts toward the space complexity of an execution if it is used in that execution. This allows us to show that many known randomized algorithms for fundamental problems in shared-memory distributed computing have expected space complexity much lower than the worst-case lower bounds, and that many algorithms that are adaptive in time complexity can also be made adaptive in space complexity. For the specific problem of mutual exclusion, we develop a new algorithm that illustrates an apparent trade-off between low expected space complexity and low expected RMR complexity. Whether this trade-off is necessary is an open problem. For some applications, it may be helpful to pay only for objects that are updated, as opposed to those that are merely read. We give a data structure that requires no space to represent objects that are not updated at the cost of a small overhead on those that are.

Cite as

James Aspnes, Bernhard Haeupler, Alexander Tong, and Philipp Woelfel. Allocate-On-Use Space Complexity of Shared-Memory Algorithms. In 32nd International Symposium on Distributed Computing (DISC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 121, pp. 8:1-8:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)


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@InProceedings{aspnes_et_al:LIPIcs.DISC.2018.8,
  author =	{Aspnes, James and Haeupler, Bernhard and Tong, Alexander and Woelfel, Philipp},
  title =	{{Allocate-On-Use Space Complexity of Shared-Memory Algorithms}},
  booktitle =	{32nd International Symposium on Distributed Computing (DISC 2018)},
  pages =	{8:1--8:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-092-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{121},
  editor =	{Schmid, Ulrich and Widder, Josef},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2018.8},
  URN =		{urn:nbn:de:0030-drops-97974},
  doi =		{10.4230/LIPIcs.DISC.2018.8},
  annote =	{Keywords: Space complexity, memory allocation, mutual exclusion}
}
Document
Recoverable FCFS Mutual Exclusion with Wait-Free Recovery

Authors: Prasad Jayanti and Anup Joshi

Published in: LIPIcs, Volume 91, 31st International Symposium on Distributed Computing (DISC 2017)


Abstract
Traditional mutual exclusion locks are not resilient to failures: if there is a power outage, the memory is wiped out. Thus, when the system comes back on, the lock will have to be restored to the initial state, i.e., all processes are rolled back to the Remainder section and all variables are reset to their initial values. Recently, Golab and Ramaraju showed that we can improve this state of the art by exploiting the Non-Volatile RAM (NVRAM). They designed algorithms that, by maintaining shared variables in NVRAM, allow processes to recover from crashes on their own without a need for a global reset, even though a crash can wipe out the local memory of a process. We present a Recoverable Mutual Exclusion algorithm using the commonly supported CAS primitive. The main features of our algorithm are that it satisfies FCFS, it ensures that each process recovers in a wait-free manner, and in the absence of failures, it guarantees a worst-case Remote Memory Reference (RMR) complexity of O(lg n) on both Cache Coherent (CC) and Distributed Shared Memory (DSM) machines, where n is the number of processes for which the algorithm is designed. This bound matches the Omega(lg n) RMR lower bound by Attiya, Hendler, and Woelfel for Mutual Exclusion algorithms that use comparison primitives.

Cite as

Prasad Jayanti and Anup Joshi. Recoverable FCFS Mutual Exclusion with Wait-Free Recovery. In 31st International Symposium on Distributed Computing (DISC 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 91, pp. 30:1-30:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)


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@InProceedings{jayanti_et_al:LIPIcs.DISC.2017.30,
  author =	{Jayanti, Prasad and Joshi, Anup},
  title =	{{Recoverable FCFS Mutual Exclusion with Wait-Free Recovery}},
  booktitle =	{31st International Symposium on Distributed Computing (DISC 2017)},
  pages =	{30:1--30:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-053-8},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{91},
  editor =	{Richa, Andr\'{e}a},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2017.30},
  URN =		{urn:nbn:de:0030-drops-80005},
  doi =		{10.4230/LIPIcs.DISC.2017.30},
  annote =	{Keywords: concurrent algorithm, synchronization, mutual exclusion, recovery, fault tolerance, non-volatile main memory, shared memory, multi-core algorithms}
}
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