From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,a5681531ca1cf09e X-Google-Attributes: gid103376,public From: fjh@mundook.cs.mu.OZ.AU (Fergus Henderson) Subject: Re: Tasking performance between Ada83 and Ada95 Date: 1997/06/25 Message-ID: <5oq70f$4f@mulga.cs.mu.OZ.AU>#1/1 X-Deja-AN: 252389541 References: <1997Jun6.115223.7384@relay.nswc.navy.mil> <7h6UFCAdNsmzEwg3@walsh.demon.co.uk> <5oir0v$mgu$1@gonzo.sun3.iaf.nl> <1997Jun23.101735.1@eisner> Organization: Comp Sci, University of Melbourne Newsgroups: comp.lang.ada Date: 1997-06-25T00:00:00+00:00 List-Id: kilgallen@eisner.decus.org (Larry Kilgallen) writes: >Geert Bosch writes: > >> IMO the best solution would be to start X system level threads and >> implement a user-level threads package on top of it. > >That is the method used by Alpha VMS. The kernel thread primitives >in fact are not documented for public consumption. The documented >interface is the DECthreads library (which has a couple different >APIs matching varying styles and standards). DECthreads creates the >user-mode lightweight threads which then get scheduled onto some >number of kernel threads (typically numbering on the order of the >number of CPUs). What happens with blocking I/O? Does DECthreads implement blocking I/O operations using asynchronous kernel I/O operations, so that it will avoid blocking a whole kernel thread when all that really needs to be blocked is a user thread? If not, then choosing the right number of kernel threads may be a bit tricky -- you want one for each CPU, to get multiprocessing, but you also need one for every user-level thread that might get blocked on I/O, so that you background compute threads don't get paused when your foreground threads are doing blocking I/O. -- Fergus Henderson | "I have always known that the pursuit WWW: | of excellence is a lethal habit" PGP: finger fjh@128.250.37.3 | -- the last words of T. S. Garp.