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: 103376,67c50b972ca3b532 X-Google-Attributes: gid103376,public From: lph@sei.cmu.edu (Larry Howard) Subject: Re: Realtime Ada Conferences Date: 1996/03/28 Message-ID: <4je56s$487@news.sei.cmu.edu>#1/1 X-Deja-AN: 144667437 references: <4jdcfd$7gc@news2.delphi.com> organization: Software Engineering Institute newsgroups: comp.lang.ada Date: 1996-03-28T00:00:00+00:00 List-Id: In article <4jdcfd$7gc@news2.delphi.com> tmoran@bix.com writes: >>Note that these context switch times are for simulated context switching >>(i.e. threads simulation), rather than for use of operating systems > > Is it just me, or does calling this a 'simulated context switch' >remind others of Orwellian language redefinition. A 'context switch' >means a switch to a different Ada task. If an implementation wants to >include switching OS threads, or rebooting to a different OS, or >switching to a different computer in orbit on the other side of the >globe, fine, but don't redefine that as a context switch and anything >else as 'simulated'. Especially in a context discussing whether a >'context switch' takes more than 20 us in a language designed for >embedded systems. > Tasking implementors, and sometimes Ada programmers, need to differentiate between tasking implementation alternatives that exhibit differing performance properties, including context switching times. I took Robert's adjectival use of "simulated" in the above quote to be no more than a designation of a particular implementation alternative. Also, a "context switch" need not refer to a switch to a _different_ task. More generally, it refers to the invocation of the scheduler to select a task to run, which may be the same task that caused the scheduling event. Excluding this possibility means that you would need another label for what is essentially the same metric. A better definition of context switching time is the elapsed time between a scheduling event and the execution of a particular task. -- Larry Howard Software Engineering Institute, Carnegie Mellon University lph@sei.cmu.edu (NeXT Mail OK) (412) 268-6397