bandwidth

Cookbook Bandwidth Example

Description

This example measures the memory bandwith capacity of GPU devices. It performs memcpy from host to GPU device, GPU device to host, and within a single GPU.

Application flow

1. User commandline arguments are parsed and test parameters initialized. If there are no commandline arguments then the test paramenters are initialized with default values.
2. Bandwidth tests are launched.
3. If the memory type for the test set to -memory pageable then the host side data is instantiated in std::vector<unsigned char>. If the memory type for the test set to -memory pinned then the host side data is instantiated in unsigned char* and allocated using hipHostMalloc.
4. Device side storage is allocated using hipMalloc in unsigned char*
5. Memory transfer is performed trail amount of times using hipMemcpy for pageable memory or using hipMemcpyAsync for host allocated pinned memory.
6. Time of memory transfer operations is measured that is then used to calculate the bandwidth.
7. All device memory is freed using hipFree and all host allocated pinned memory is freed using hipHostFree.

Key APIs and Concepts

The program uses HIP pageable and pinned memory. It is important to note that the pinned memory is allocated using hipHostMalloc and is destroyed using hipHostFree. The HIP memory transfer routine hipMemcpyAsync will behave synchronously if the host memory is not pinned. Therefore, it is important to allocate pinned host memory using hipHostMalloc for hipMemcpyAsync to behave asynchronously.

Demonstrated API Calls

HIP runtime

• hipMalloc
• hipMemcpy
• hipMemcpyAsync
• hipGetDeviceCount
• hipGetDeviceProperties
• hipFree
• hipHostFree
• hipHostMalloc
• hipSetDevice