Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!ucsd!ucsdhub!esosun!seismo!uunet!vsi!friedl From: friedl@vsi.UUCP (Stephen J. Friedl) Newsgroups: comp.sys.att Subject: Help with system lockup Message-ID: <813@vsi.UUCP> Date: 20 Aug 88 15:54:37 GMT Followup-To: poster Distribution: comp Organization: V-Systems, Inc. -- Santa Ana, CA Lines: 38 Hi folks, I've a customer with a 3B2/300 running Sys V Rel 3. We just upgraded their machine to use 4MB of RAM and we're having some strangeness, the source of which I'm not sure. The system runs much better with the new RAM, but on occassion it just locks up for several seconds at a time. This is, as you might imagine, annoying, and the customer has politely inferred that this is somehow our doing. Running pmon shows that the system is very busy, with `cpu split information' showing just User and Kernel time (no Idle at all). At lockup, however, the system goes into `Wait' state, and the `Wait time breakdown' shows 100% I/O. Turning to the other screens, the system memory usage is approaching 100% (4MB). I never saw a lockup while looking at the memory screen, but I'm guessing that hitting 100% was causing this. We also occasionally get `cannot fork' errors on various terminals when memory is tight. Questions: First, what exactly is `wait' time. I have a general idea but not the specific definition. Second, in a virtual-memory machine, why should hitting the wall on physical memory be such a big hit? We have plenty of swap space split on two spindles, and I would have assumed that paging activity would rise slowly, not this suddenly. I believe this may be related to the virtual memory parameters, but I'm not that smart... Please, any insights into this would be really helpful. Steve -- Steve Friedl V-Systems, Inc. +1 714 545 6442 3B2-kind-of-guy friedl@vsi.com {backbones}!vsi.com!friedl attmail!vsi!friedl ---------Nancy Reagan on the Three Stooges: "Just say Moe"---------