The simple answer is that these lanes (buffers, I prefer to call them) are per logical core. The more complicated answer is that there are a variety of buffers

The simple answer is that these lanes (buffers, I prefer to call them) are per logical core. The more complicated answer is that there are a variety of buffers involved in the "path to memory", starting with the core-private buffers between the core and L1 and L2, and moving to socket-shared buffers at the L3, memory controllers and DRAM. In this particular single-threaded test, it is the 10 core-private "line fill buffers" between the L1 and L2 which are the bottleneck, which is where you get the simple answer from. If you ran this test on enough cores at the same time, I would entirely expect the bottlneck to change to one of the shared buffers.