Avoid frequency drop in GPU cores when executing applications in Heterogeneous mode

Introduction

Intel(R) C++ Compiler 15.0 provides a feature which enables offloading general purpose compute kernels to processor graphics. This feature enables the processor graphics silicon area for general purpose computing. The key idea is to utilize the compute power of both CPU cores and GPU execution units in tandem for better utilization of available compute power.

Target OS requirements:

Windows* 32 and 64 bit support. Compute offload feature on Microsoft Windows 7* will only work with an active display (no locked screen). This restriction is imposed by DirectX 9 but relaxed in DirectX 11 (on Microsoft Windows 8* and Microsoft Windows 8.1*). 

Linux 64 bit:

1. Ubuntu 12.04 (Linux kernel numbers: 3.2.0-41 for 3rd generation Intel® Core™ Processors and 3.8.0-23 for 4th generation Intel® Core™ Processors)
2. SUSE Linux Enterprise Server 11 SP3 (Linux kernel numbers: 3.0.76-11 for both 3rd and 4th generation Intel® Core™ Processors) 

Heterogeneous mode

When executing an application in heterogeneous mode (CPU+GPU cores in action), the processor is running in full throttle. Every processor has an operating TDP limit and the power sharing algorithm implemented in hardware will take the necessary action to keep the processor within the TDP limits. Modern processors having both Intel(R) Turbo Boost Technology and Intel(R) HD Graphics Dynamic Frequency Technology. Intel(R) Turbo Boost Technology is used for increasing the frequency of the CPU cores when needed. Intel(R) HD Graphics Dynamic Frequency Technology is something similar to Turbo boost for GPU cores. When both CPU and GPU are in action simultaneously, that's when processor is hitting TDP limits relatively quicker. In these cases, for the default power settings on the system ("Maximize Performance" or "balanced" for CPU, Turbo Boost turned ON and "Balanced" for GPU), the power sharing algorithm gives preference to CPU core's frequency. Section 2.3 in http://www.intel.com/Assets/PDF/whitepaper/323324.pdf describes how to avoid drop in GPU core frequency. In short, do the following:

1. Turn off Intel(R) Turbo Boost Technology
2. Switch the power option of Graphics processor from "Balanced" to "Maximize Performance"

This user control helps in giving the priority for GPU cores for workloads which performs better on GPU.

This article applies to:
    Products: Intel® System Studio
    Host OS/Platform: Windows (IA-32 or Intel® 64); Linux (Intel® 64)
    Target OS/platform: Windows (IA-32 or Intel® 64); Ubuntu 12.04 (Intel® 64)