Generalizing a bit from the wikipedia article:
Minor page fault:
"If the page is loaded in memory at the time the fault is generated, but is not marked in the memory management unit as being loaded in memory, then it is called a minor or soft page fault. The page fault handler in the operating system merely needs to make the entry for that page in the memory management unit point to the page in memory and indicate that the page is loaded in memory; it does not need to read the page into memory. "
We could distinguish between these two types based on whether they involve reading the page into memory from a backing store. In GPU UM usage, the backing store is the memory of another processor in the heterogeneous system, rather than secondary storage (disk) in the traditional sense/usage.
This sort of (“minor”) page-faulting may occur in a UM scenario after initial allocation of the page(s).
After calling cudaMallocManaged, if the cpu code touches the page (first) that was just allocated, then a CPU page fault will occur (this can be confirmed using a profiler). This sort of cpu page fault does not result in any UM migration (copying) of data. It is more like the lazy allocation process that the host operating system (may) use:
Lazy allocation results in allocated (i.e. reserved) but unmapped memory. The process of the CPU writing to this memory creates a mapping, whereafter it is ordinarily usable by the host code.
In this sense, I think you could refer to this sort of page fault in a UM system as a “minor” page fault. It would be distinguished from a “major” page fault, wherein the page is currently not resident and mapped to another processor’s memory space. In that case, the page fault results in a copying of data.
A similar page-fault-with-no-copy scenario can be identified in the profiler, if the memory is allocated e.g. with cudaMallocManaged, and the first processor to touch it (i.e. write to it) is the GPU.
This is just my opinion/$0.02. I’m not suggesting that this is in any way standard terminology. I merely offer this as a view point or discussion point.