Abstract
Task-based programming models are excellent tools to parallelize and seamlessly load balance an application workload. However, the integration of I/O intensive applications and task-based programming models is lacking. Typically, I/O operations stall the requesting thread until the data is serviced by the backing device. Because the core where the thread was running becomes idle, it should be possible to overlap the data query operation with either computation workloads or even more I/O operations. Nonetheless, overlapping I/O tasks with other tasks entails an extra degree of complexity currently not managed by programming models’ runtimes. In this work, we focus on integrating storage I/O into the tasking model by introducing the Task-Aware Storage I/O (TASIO) library. We test TASIO extensively with a custom benchmark for a number of configurations and conclude that it is able to achieve speedups up to 2x depending on the workload, although it might lead to slowdowns if not used with the right settings.
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Notes
- 1.
The operation might return immediately, i.e. not block, if the system page cache already holds the requested data in the case of reads or if the page cache has enough free space as to defer the operation for a later time in the case of writes.
- 2.
A context is basically a queue of requests.
- 3.
The low level details of such APIs can be consulted in [10].
- 4.
Smarter techniques could be used, but because this is a corner case we have simplified it for now.
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Acknowledgment
This project is supported by the European Union’s Horizon 2021 research and innovation programme under the grant agreement No 754304 (DEEP-EST), the Ministry of Economy of Spain through the Severo Ochoa Center of Excellence Program (SEV-2015-0493), by the Spanish Ministry of Science and Innovation (contract TIN2015-65316-P) and by the Generalitat de Catalunya (2017-SGR-1481). Also, the authors would like to acknowledge that the test environment (Cobi) was ceded by Intel Corporation in the frame of the BSC - Intel collaboration.
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Roca Nonell, A., Beltran Querol, V., Mateo Bellido, S. (2019). Introducing the Task-Aware Storage I/O (TASIO) Library. In: Fan, X., de Supinski, B., Sinnen, O., Giacaman, N. (eds) OpenMP: Conquering the Full Hardware Spectrum. IWOMP 2019. Lecture Notes in Computer Science(), vol 11718. Springer, Cham. https://doi.org/10.1007/978-3-030-28596-8_19
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