[HECnet] A2RTR downtime

I couldn't say whether it was "much", but I can definitely say that it wasn't "if ever".? If you will look at GLXMEM, the GLXLIB memory manager, you will see that it implements a page fault handler.? It does this to keep its un-shared page usage (what would be considered the low segment) quite low.? When garbage collection happens, private memory is trimmed down to (I believe) 7 pages. The reason for the page handler is to allow for greater ease of implementation of the linked list manager; that is, you don't have to 'burp' the memory to get rid of holes, you just ditch the page. This is completely different from the Tops-20 GLXMEM, which couldn't care less.? It results more usage of the backing store (what is called the paging 'drum') which really shouldn't hurt anything, normally.? However, if you are writing big piggy extended mode programs like I do, then you can exhaust the backing page store, even on a hobbyist system.? This happens to me because my programming style always trades space for time as I don't currently have any prospects of multi-CPU Tops-20. I liked Tops-10's GLXMEM handler so much that I adapted it for use on Tops-20 GLXMEM.? When the garbage collector gets triggered, I delete the pages from the address space to free drum storage. Nice. Sections on Tops-20 are altogether different; they have to be explicitly created and you can write the equivalent of a page handler to do this outside of regular program memory management. I think I've done it in one program. The Tops-10 VM manager paradigm comes in two flavors: you can use Tops-10's default manager or you can override that to handle the page faults your own with the PAGE. UUO.? Not sure I'd call that "special", but it is nice not to have to be bothered with it if you don't feel like it. How 'stupid' did you guys get?? I think the worst I ever heard was a very, very, very long chain of indirect memory reference. Since the EA has to be calculated and resolved before the opcode can be handled, you can get the situation that you can be paging to do that calculation only to be stopped by a clock interrupt which then dismisses back into the same instruction, which has to be restarted, over and over again. Pretty anti-social usually, I'd have to say, but probably a fantastic way to slam the hardware around for burn-in. On 10/18/21 10:58 PM, Robert Armstrong wrote: