On Mon, Apr 23, 2018 at 1:30 PM, Ron Natalie <ron@ronnatalie.com> wrote:

Ø Well, I had known but forgotten in fact. There's also a distinction between whether a system swaps/pages onto a dedicated device and whether it exposes that device by some special name in /dev.

I’m pretty sure that swapping in V6 took place to a major/minor number configured at kernel build time. You could create a dev node for the swap device, but it wasn’t used for the actual swapping.

Exactly... For instance an RK04 was less that 5K blocks (4620 or some such - I've forgotten the actually amount). The disk was mkfs'ed to the first 4K and the left over was give to the swap system. By the time of 4.X, the RP06 was 'partitioned' into 'rings' (some overlapping). The 'a' partition was root, the 'b' was swap and one fo the others was the rest. Later the 'c' was a short form for copying the entire disk.

What /dev/drum did was allow to cobble up those hunks of reserved space and view them as a single device. I've forgotten what user space programs used it, probably some of the tools like ps, vmstat etc. You'd have to look that the sources.