Re: [TUHS] History of top

On Thu, May 24, 2018 at 5:20 AM, Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote: around at different UNIX sites. CMU's locally hacked ps was similar to dpy and BSD's *stat programs (systatm vmstat, ...). The problem all of these had was getting the data out of the OS. The original scheme used by ps being it ran setuid/gid, and then was able to opening /dev/kmem and reading interesting data structures the kernel. A big problem was that ps and the OS had to be compiled with exactly the same headers and you really had to know the layout and the obvious security concerns of using setuid/gid to control things. FreeBSD's sysctl and V8's /proc would finally clean that up by making a formal interface to the OS and controlling what was available in a more granular manner both from a data structure as well as security path. Although before /proc came to being (/proc was a UNIX innovation), the sysctl(2) like interface was reinvented a few times, as it really was not new with UNIX. It's very much like a similar scheme that came from TOPS, RSX and VMS (which the Masscomp system parroted being ex-DECies almost exactly the same as VMS). I believe that Sun had something also, but I've forgotten its name, Larry might remember. But so did DG-OS and many of the other commercial UNIXs snd I would not be surprised if many University hacks did it also. My favorite of all of these was the one that George Gobble at Purdue built when he did the Dual VAX. He also spliced an PDP-11 on the UBA on the their Dual Vax System and wrote a program that like top(1) refreshed itself (at least as fast as once a sec IIRC). It would read the VAX memory and then display what the OS was doing in real time. He did a neat talk in a mid-1980's USENIX with a movie from it. They found an interesting bug in the BSD scheduler which had been there since 6th edition, which had never really been noticed until people could visually watch what as happening and actually get enough information about how processes were being handled. [This was also around the time one of the first '0-day' issues with UNIX was found by ghg and team which is now a cute story but at the time was quite worrisome]. ​The best I remember, the popularity of top(1) started because it was first released as USENET came of age; and thus it got wide distribution. By that point, ​ *BSD was the 'standard' in most places, and this the *stat commands were pretty well known. The top(1) program consolidated these into a single one, plus it used the curses library so it could be left running on a glass TTY. As Vaxen were being used as large timesharing systems for Universities to teach with, such a program was handy for the sys admins to keep an eye on what was happening. Clem ᐧ