Hybrid Approach Could Boost Graphics Processing Speeds

Multicore processors have provided a significant boost for graphics processing, but researchers at North Carolina State University are taking things a step further by boosting multicore CPU performance by an average of more than 20%.

Called CPU-assisted general purpose computation on graphics processor units (CPU-assisted GPGPU), the technology under development at NCSU allows both units to collaborate on a computing task. This approach is designed for fused architecture chipsets with a shared level-3 cache and shared off-chip memory for CPUs and GPUs.

The research, conducted through the school’s Department of Electrical and Computer Engineering, was funded by grants from the National Science Foundation and AMD.

Although hybrid CPU/GPU systems improve energy efficiency, the cores primarily work on separate functions. The NCSU team wanted to improve processing functionality by having the CPU’s L3 cache pre-fetch and feed data to the GPU, so that process threads running in the GPU go directly to the L3 cache, reducing latency.

According to Dr. Huiyang Zhou:

 This is more efficient because it allows CPUs and GPUs to do what they are good at. GPUs are good at performing computations. CPUs are good at making decisions and flexible data retrieval.

CPUs and GPUs fetch data from off-chip main memory at approximately the same speed, but GPUs  execute the functions that use that data more quickly. By having the CPU determine what the GPU will need in advance, the GPU can focus on execution. In preliminary testing, performance has improved by an average of 21.4%. So far, though, this performance has only been documented in simulations, because the current hybrid processors (AMD’s Llano and Intel’s Sandy Bridge) either lack a shared L3 cache or have limited hybrid functionality.

The team will present “CPU-Assisted GPGPU on Fused CPU-GPU Architectures” on Feb. 27 at the 18h International Symposium on High Performance Computer Architecture in New Orleans.

Source: North Carolina State University

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