Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!ll-xn!mit-eddie!rutgers!aramis.rutgers.edu!athos.rutgers.edu!hedrick From: hedrick@athos.rutgers.edu (Charles Hedrick) Newsgroups: comp.unix.wizards Subject: Re: Berkeley paging Message-ID: Date: 20 May 88 02:29:08 GMT References: <53@lazlo.UUCP> <142700033@occrsh.ATT.COM> <651@pyuxe.UUCP> <7878@brl-smoke.ARPA> <11484@mimsy.UUCP> <7891@brl-smoke.ARPA> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 21 When discussing SV vs BSD paging, it's interesting to look at the comparison of TOPS-20 with other DEC OS's (VMS and TOPS-10). SV has been compared to VMS (note that I don't know anything independent about it, since I know only SVr2 without paging). In many ways BSD looks more like TOPS-20. The claim was always made that VMS paging, like TOPS-10 paging, was more efficient than TOPS-20 because processes paged only "against themselves". It always seemed that in practice, good performance on VMS requires more adjustment of user-specific parameters. On TOPS-10 (where I have more detailed experience, though years out of date), it seemed that system performance had more of a "knee". With one process paging, the system really did protect other processes against it, but when several processes paged, because no global resource computations were made, you ended up using up all the disk bandwidth, and everybody died. (Of course this may have improved after I left the TOPS-10 community, which is many years ago.) TOPS-20 definitely had more of an overhead than TOPS-10 or VMS, but required no tuning and overloaded "soft". One suspects something similar is likely to be true of BSD vs. SV: that neither is universally superior, but rather than they each have advantages in different circumstances. It might be useful to try to characterize those circumstances rather than decide which is "better". Does anybody know both well enough to have a go at it?