Soriano-Salvador, EnriqueGuardiola Múzquiz, GorkaBallesteros, Francisco J.2023-11-102023-11-102015Soriano-Salvador, E., Muzquiz, G. G., and Ballesteros, F. J. (2015) Optimistic semaphores with non-deterministic choice operation for heterogeneous manycore systems. Concurrency Computat.: Pract. Exper., 27: 3676–3701.3676–3701https://hdl.handle.net/10115/25804The Nix operating system permits different roles to be assigned to the cores. One of the roles is to be able to run user-space code with no interrupts from the operating system, which is particularly useful for high-performance computing. System calls are especially expensive to a core playing this role. This paper presents a new implementation of optimistic semaphores that avoid performing expensive system calls in an uncontended scenario. The implementation is straightforward and somewhat unorthodox: a semaphore is based on a data structure and a lock that are shared between user space and kernel space. This study aims at evaluating if such an approach is viable. In addition, the implementation includes a non-deterministic choice operation over a collection of semaphores, altsems. This novel operation facilitates the creation of higher-level communication mechanisms, such as sockets and channels. To support this claim, we implemented a new kind of buffered communication channels named tubes, tailored for communicating processes running on different (heterogeneous) cores. The paper describes the implementation of the semaphores and the tubes, a comparative analysis of optimistic and non-optimistic semaphores on Nix, and a comparative analysis of tubes and other kinds of communication channels that are available on the Nix operating system. Copyright © 2014 John Wiley & Sons, Ltd.engOperating systemsConcurrencySemaphoreManycoreinfo:eu-repo/semantics/article10.1002/cpe.3363info:eu-repo/semantics/openAccess