Ultra Etherent: Discovery
Creating the fi_info Structure
Before the application can discover what communication services are available, it first needs a way to describe what it is looking for. This description is built using a structure called fi_info. The fi_info structure acts like a container that holds the application’s initial requirements, such as desired endpoint type or capabilities.
The first step is to reserve memory for this structure in the system’s main memory. The fi_allocinfo() helper function does this for the application. When called, fi_allocinfo() allocates space for a new fi_info structure, which this book refers to as the pre-fi_info, that will later be passed to the libfabric core for matching against available providers.
At this stage, most of the fields inside the pre-fi_info structure are left at their default values. The application typically sets only the most relevant parameters that express what it needs, such as the desired endpoint type or provider name, and leaves the rest for the provider to fill in later.
In addition to the main fi_info structure, the helper function also allocates memory for a set of sub-structures. These describe different parts of the communication stack, including the fabric, domain, and endpoints. The fixed sub-structures Continue reading
