Titel:
Direct Communication Methods for Distributed GPUs
Beteiligte:
Oden, Lena
[Verfasser:in]
Erschienen:
Heidelberg University: HeiDok, 2015
Sprache:
Englisch
DOI:
https://doi.org/10.11588/heidok.00018623
Entstehung:
Anmerkungen:
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Beschreibung:
Today, GPUs and other parallel accelerators are widely used in high performance computing, due to their high computational power and high performance per watt. Still, one of the main bottlenecks of GPU-accelerated cluster computing is the data transfer between distributed GPUs. This not only affects performance, but also power consumption. Often, a data transfer between two distributed GPUs even requires intermediate copies in host memory. This overhead penalizes small data movements and synchronization operations. In this work, different communication methods for distributed GPUs are implemented and evaluated. First, a new technique, called GPUDirect RDMA, is implemented for the Extoll device and evaluated. The performance results show that this technique brings performance benefits for small- and mediums-sized data transfers, but for larger transfer sizes, a staged protocol is preferable since the PCIe-bus does not well support peer-to-peer data transfers. In the next step, GPUs are integrated to the one-sided communication library GPI-2. Since this interface was designed for heterogeneous memory structures, it allows an easy integration of GPUs. The performance results show that using one-sided communication for GPUs brings some performance benefits compared to two-sided communication which is the current state-of-the-art. However, using GPI-2 for communication still requires a host thread to control GPU-related communication, although the data is transferred directly between the GPUs without any host copies. Therefore, the subsequent part of the work analyze GPU-controlled communication. First, a put/get communication interface, based on Infiniband verbs, for the GPU is implemented. This interface enables the GPU to independently source and synchronize communication requests without any involvements of the CPU. However, the Infiniband verbs protocol adds a lot of sequential overhead to the communication, so the performance of GPU-controlled put/get communication is far behind the performance of ...