DynAMO: Improving parallelism through dynamic placement of atomic memory operations

With increasing core counts in modern multi-core designs, the overhead of synchronization jeopardizes the scalability and efficiency of parallel applications. To mitigate these overheads, modern cache-coherent protocols offer support for Atomic Memory Operations (AMOs) that can be executed near-core (near) or remotely in the on-chip memory hierarchy (far). This paper evaluates current available static AMO execution policies implemented in multi-core Systems-on-Chip (SoC) designs, which select AMOs' execution placement (near or far) based on the cache block coherence state. We propose three static policies and show that the performance of static policies is application dependent. Moreover, we show that one of our proposed static policies outperforms currently available implementations. Furthermore, we propose DynAMO, a predictor that selects the best location to execute the AMOs. DynAMO identifies the different locality patterns to make informed decisions, improving AMO latency and increasing overall throughput. DynAMO outperforms the best-performing static policy and provides geometric mean speed-ups of 1.09× across all workloads and 1.31× on AMO-intensive applications with respect to executing all AMOs near.This research was supported by the Spanish Ministry of Science and Innovation (MCIN) through contracts [PID2019-107255GB-C21], [TED2021-132634A-I00], and [PID2019-105660RB-C21]; the Generalitat of Catalunya through contract [2021-SGR-00763]; the Government of Aragon [T5820R]; the Arm-BSC Center of Excellence, and the European Processor Initiative (EPI) which is part of the European Union’s Horizon 2020 research and innovation program under grant agreement No. 826647. V. Soria-Pardos has been supported through an FPU fellowship [FPU20-02132]; A. Armejach is a Serra Hunter Fellow and has been partially supported by the Grant [IJCI-2017-33945] funded by MCIN/AEI/10.13039/501100011033; M. Moreto through a Ramón y Cajal fellowship [RYC-2016-21104].Peer ReviewedPostprint (author's final draft