Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!decwrl!ogicse!ucsd!sdcc6!beowulf!velasco From: velasco@beowulf.ucsd.edu (Gabriel Velasco) Newsgroups: comp.os.mach Subject: Re: Threads, Definition of Message-ID: Date: 9 Feb 91 02:05:38 GMT References: <4964@umbc3.UMBC.EDU> <1476@pdxgate.UUCP> Sender: news@sdcc6.ucsd.edu Lines: 38 Nntp-Posting-Host: beowulf.ucsd.edu berggren@eecs.cs.pdx.edu (Eric Berggren) writes: >dmason@msg.uwaterloo.ca (Dave Mason) writes: >>As I'm supposed to be working on a paper about this at this very >>moment, rather than reading news (-: >>Lightweight processes are processes that share an address space. >>The implications, ramifications and implementations of this vary >>wildly. Implementations of lwp's on Unix systems vary from Sun lwp's >>and the uSystem where several lwp's share a Unix process and the >>operating system knows nothing of their existence, through Mach >>threads which are almost as lightweight as they can get with the >>operating system knowing about them, up to systems where lwp's are ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >>effectively full Unix processes which have mapped a common area of >>memory to work with. > How, exactly, does this differ from shared memory processes? >Thanx. The operating system knows about threads. This is not necessarily the case with light-weight processes. With the first kind of light-weight processes that Dave mentions above, all of the light-weight processes have to share the time alloted to the one Unix process within which they were created. The Unix process takes care of any scheduling that needs to be done by dividing up the time that is alloted to it. The operating system really needs to know about individual threads of execution to properly schedule them on a multiprocessor system and to avoid things like all of the other light-weight processes within a Unix-like process blocking when one of them does. -- ________________________________________________ <>___, / / | ... and he called out and said, "Gabriel, give | /___/ __ / _ __ ' _ / | this man an understanding of the vision." | /\__/\(_/\/__)\/ (_/_(/_/|_ |_______________________________________Dan_8:16_|