[TUHS] Re: LSX issues and musing

{I was going to reply to an earlier message, but my CFS left me with insufficient energy; I'll try and catch up on the points I was goibf to make here.} I'm curious how much memory you have in your target system; it must not be a lot, if you're targeting LSX. I ask because LSX has been somewhat 'lobotimized' (I don't mean that in a negative way; it's just recognition that LSX has had a lot of corners trimmed, to squeeze it down as much as possible), and some of those trims behind some of the issues you're having (below). At the time the LSI-11 came out, semiconductor DRAM was just getting started, so an LSI-11 with 8KB onboard and a 32KB DRAM card (or four 8KB MMV11 core memory cards :-), to produce the 40KB target for LSX systems, was then a reasonable configuration. These days, one has to really search to find anything smaller than 64KB... It might be easier to just run MINI-UNIX (which is much closer to V6, and thus a known quantity), than add a lot of things back in to LSX to produce what will effectively be MINI-UNIX; even if you have to buy a bit more QBUS memory for the machine. And here you're seeing the 'lobotomizing' of LSX come into play. That '101' made me suspicious, as the base V6 'caches' 100 free inodes in the super-block; once those are used, it scans the ilist on disk to refill it. The code in alloc$ialloc in LSX is hard to understand (there are a lot of #ifdef's), and it's very different from the V6 code, but I'm pretty sure it doesn't refill the 'cache' after it uses the cached 100 free inodes. So, you can have as many free inodes on a disk as you want, but LSX will never use more than the first 100. (Note that the comment in the LSX source "up to 100 spare I nodes in the super block. When this runs out, a linear search through the I list is instituted to pick up 100 more." is inaccurate; it probably wasn't updated after the code was changed. ISTR tis is true of a lot of the comments.) Use MINI-UNIX. The V6 'mkfs' does not fill the free inode cache in the super-block. So, it's empty when you start out. The LSX ialloc() says: if(fp->s_ninode > 0) { ... } u.u_error = ENOSPC; return(NULL); which would produce what you're seeing. Also, another problem with trying to 'push' LSX into a previously un-handled operating regions (e.g. large disks, but there are likely others) is that there are probably things that are un-tested in that previously unused operating mode, and there may be un-found bugs that you trip across. Use MINI-UNIX. I had a look at the source (in sys4.c, nami.c, iget.c, rdwri.c, and alloc.c), but I couldn't quickly find the cause; it isn't obvious. (When unlinking a file, the blocks in the file have to be freed - that's inode 'ip' - and the directory - inode 'pp' - has to be updated; so it's pretty complicated.) Use MINI-UNIX. My recollection is that the LSX kernel doesn't have code to create contiguous files; the LSX page at the CHWiki says "the paper describing LSX indicates there were two separate programs, one to allocate space for such files, and one to move a file into such an area, but they do not seem to be extant". If you find them, could you let me know? Thanks. Noel