Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!convex!swarren From: swarren@convex.com (Steve Warren) Newsgroups: comp.sys.amiga.advocacy Subject: Re: Single user OS schedulers (Was Re: How do we change the scheduler?) Message-ID: <1991Jan25.161048.8420@convex.com> Date: 25 Jan 91 16:10:48 GMT References: <1991Jan23.213736.28220@Neon.Stanford.EDU> <1991Jan24.152931.1325@NCoast.ORG> <1991Jan25.073516.29644@Neon.Stanford.EDU> Sender: usenet@convex.com (news access account) Organization: Convex Computer Corporation, Richardson, Tx. Lines: 44 Nntp-Posting-Host: neptune.convex.com In article <1991Jan25.073516.29644@Neon.Stanford.EDU> torrie@cs.stanford.edu (Evan J Torrie) writes: [...] > Yes, but this raises another issue. In this case, you are running a >task which is servicing other users... effectively, you want your >scheduler to give good multiuser response [i.e. no starvation]. > For these cases, Unix-like schedulers (which it seems the Amiga >scheduler is modeled after, judging by the description so far) are >definitely the right choice (after all, a lot of work has been put >into researching the best scheduling systems for MULTI-USER OSes) [...] Hmm, I think you are getting an unclear picture of the Amiga multitasking mechanism. My understanding is that Amiga multitasking is different from UNIX precisely in that it was designed to give real-time single-user response. That is one reason there are not multi-user provisions built-in to the OS. One of the first things I noticed when I started using a Sun workstation at work was how poor the user response was when compared to a 68000-based Amiga. I have since learned that this is a function of the way UNIX implements its scheduler vs the way the Amiga does it. The Sun of course is able (with a 68030) to do more things at the same time than the 68000 based Amiga. But sometimes my Amiga seems faster because the OS puts more emphasis on fast user response. I understand that because coprocessors are able to handle much of the user response (through sprite implementation of the mouse cursor, for example), that very little of the total CPU resources are needed to provide snappy response, especially at the workbench level. The CPU does not have to busy-wait for input, of course. Sorry there are not more details here. I am only qualified to discuss this in terms of user-perception, not in terms of low-level OS operations. But I have seen qualified individuals contrast the Unix scheduler with the Amiga scheduler, with the conclusion that the Amiga scheduler is designed to provide real-time single-user response, unlike the Unix scheduler. -- _. --Steve ._||__ DISCLAIMER: All opinions are my own. Warren v\ *| ---------------------------------------------- V {uunet,sun}!convex!swarren; swarren@convex.com