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From: Richard.Draves@CS.CMU.EDU
Newsgroups: comp.misc
Subject: Re: A tirade about inefficient software & systems
Message-ID: <YbBQ_1G00hsQFaf1E=@cs.cmu.edu>
Date: 5 Nov 90 19:50:25 GMT
References: <1990Nov1.002513.8984@ico.isc.com> <608@escom.com> <1990Nov2.203059.13930@ico.isc.com>,
	<8561@scolex.sco.COM>
Organization: Carnegie Mellon, Pittsburgh, PA
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In-Reply-To: <8561@scolex.sco.COM>

> Excerpts from netnews.comp.misc: 4-Nov-90 Re: A tirade about ineffici..
> Sean Fagan@sco.COM (1461)

> One of the points mentioned that a way to slow down an OS is to have
> lots of
> context switches.  I agree; Mach is certainly worse in that respect than,
> say, SysV.  However, just like the CISC vs. RISC debate, there's
> something
> else to note: Mach has *quicker* context switches than generic Unix (and
> that's why a BSD program, given the same hardware, only different OS's,
> will
> run faster under Mach than SunOS [study done at CMU]).


Why do you think Mach has more context-switches than SysV?  I think the
reason Mach generally does better than SunOS or Ultrix has very little
to do with context-switch performance.  In general, important operations
like fork/exec are faster, and the VM system does a better job of
caching data.

Rich